diff --git a/test/built-ins/Temporal/Calendar/prototype/dateAdd/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/dateAdd/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..d285863cbd5
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dateAdd/argument-string-unknown-annotation.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dateadd
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.dateAdd(arg, new Temporal.Duration());
+
+  TemporalHelpers.assertPlainDate(
+    result,
+    2000, 5, "M05", 2,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/dateUntil/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/dateUntil/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..3b83c67e5fb
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dateUntil/argument-string-unknown-annotation.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dateuntil
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.dateUntil(arg, arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/day/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/day/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..40038e90dac
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/day/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.day
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.day(arg);
+
+  assert.sameValue(
+    result,
+    2,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/dayOfWeek/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/dayOfWeek/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..806494ecf37
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dayOfWeek/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dayofweek
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.dayOfWeek(arg);
+
+  assert.sameValue(
+    result,
+    2,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/dayOfYear/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/dayOfYear/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..dbeb37d96f8
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dayOfYear/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dayofyear
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.dayOfYear(arg);
+
+  assert.sameValue(
+    result,
+    123,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/daysInMonth/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/daysInMonth/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..8541062e59f
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/daysInMonth/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.daysinmonth
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.daysInMonth(arg);
+
+  assert.sameValue(
+    result,
+    31,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/daysInWeek/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/daysInWeek/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..56f900bb369
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/daysInWeek/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.daysinweek
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.daysInWeek(arg);
+
+  assert.sameValue(
+    result,
+    7,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/daysInYear/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/daysInYear/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..12c900339c3
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/daysInYear/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.daysinyear
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.daysInYear(arg);
+
+  assert.sameValue(
+    result,
+    366,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/inLeapYear/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/inLeapYear/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..539fe4533a8
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/inLeapYear/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.inleapyear
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.inLeapYear(arg);
+
+  assert.sameValue(
+    result,
+    true,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/month/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/month/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..6a966dfced8
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/month/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.month
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.month(arg);
+
+  assert.sameValue(
+    result,
+    5,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/monthCode/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/monthCode/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..ed3ef4d428e
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/monthCode/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.monthcode
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.monthCode(arg);
+
+  assert.sameValue(
+    result,
+    "M05",
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/monthsInYear/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/monthsInYear/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..118150626ed
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/monthsInYear/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.monthsinyear
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.monthsInYear(arg);
+
+  assert.sameValue(
+    result,
+    12,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/weekOfYear/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/weekOfYear/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..951d276a1c8
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/weekOfYear/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.weekofyear
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.weekOfYear(arg);
+
+  assert.sameValue(
+    result,
+    18,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Calendar/prototype/year/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Calendar/prototype/year/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..e6ab34eeeeb
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/year/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.year
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.year(arg);
+
+  assert.sameValue(
+    result,
+    2000,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Instant/compare/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Instant/compare/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..08c761a6dd1
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/compare/argument-string-unknown-annotation.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.compare
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00Z[foo=bar]", "alone"],
+  ["1970-01-01T00:00Z[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00Z[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1970-01-01T00:00Z[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1970-01-01T00:00Z[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.Instant.compare(arg, arg);
+
+  assert.sameValue(
+    result,
+    0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Instant/from/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Instant/from/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..f51a241adca
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/from/argument-string-unknown-annotation.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.from
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00Z[foo=bar]", "alone"],
+  ["1970-01-01T00:00Z[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00Z[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1970-01-01T00:00Z[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1970-01-01T00:00Z[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.Instant.from(arg);
+
+  assert.sameValue(
+    result.epochNanoseconds,
+    0n,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Instant/prototype/equals/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Instant/prototype/equals/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..2d1ee64f9f3
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/equals/argument-string-unknown-annotation.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.equals
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00Z[foo=bar]", "alone"],
+  ["1970-01-01T00:00Z[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00Z[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1970-01-01T00:00Z[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1970-01-01T00:00Z[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Instant(0n);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.equals(arg);
+
+  assert.sameValue(
+    result,
+    true,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Instant/prototype/since/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Instant/prototype/since/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..0c032c524aa
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/since/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.since
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00Z[foo=bar]", "alone"],
+  ["1970-01-01T00:00Z[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00Z[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1970-01-01T00:00Z[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1970-01-01T00:00Z[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Instant(0n);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.since(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/Instant/prototype/until/argument-string-unknown-annotation.js b/test/built-ins/Temporal/Instant/prototype/until/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..2816b6035af
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/until/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.until
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00Z[foo=bar]", "alone"],
+  ["1970-01-01T00:00Z[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00Z[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1970-01-01T00:00Z[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1970-01-01T00:00Z[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Instant(0n);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.until(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDate/compare/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDate/compare/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..9bd1428f74f
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/compare/argument-string-unknown-annotation.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.compare
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.PlainDate.compare(arg, arg);
+
+  assert.sameValue(
+    result,
+    0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDate/from/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDate/from/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..f08ca2ca9fd
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/from/argument-string-unknown-annotation.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.from
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.PlainDate.from(arg);
+
+  TemporalHelpers.assertPlainDate(
+    result,
+    2000, 5, "M05", 2,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDate/prototype/equals/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDate/prototype/equals/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..9eefcba2125
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/equals/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.equals
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainDate(2000, 5, 2);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.equals(arg);
+
+  assert.sameValue(
+    result,
+    true,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDate/prototype/since/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDate/prototype/since/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..a1f9dab3850
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/since/argument-string-unknown-annotation.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.since
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainDate(2000, 5, 2);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.since(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDate/prototype/toPlainDateTime/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDate/prototype/toPlainDateTime/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..482a705eeba
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/toPlainDateTime/argument-string-unknown-annotation.js
@@ -0,0 +1,37 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.toplaindatetime
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["12:34:56.987654321[foo=bar]", "alone"],
+  ["12:34:56.987654321[UTC][foo=bar]", "with time zone"],
+  ["12:34:56.987654321[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["T12:34:56.987654321[foo=bar]", "with T"],
+  ["T12:34:56.987654321[UTC][foo=bar]", "with T and time zone"],
+  ["T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with T and calendar"],
+  ["T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with T, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar]", "with date"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar]", "with date and time zone"],
+  ["1970-01-01T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with date and calendar"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with date, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainDate(2000, 5, 2);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.toPlainDateTime(arg);
+
+  TemporalHelpers.assertPlainDateTime(
+    result,
+    2000, 5, "M05", 2, 12, 34, 56, 987, 654, 321,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..3ac8970b0a0
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/argument-string-unknown-annotation.js
@@ -0,0 +1,36 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.tozoneddatetime
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["12:34:56.987654321[foo=bar]", "alone"],
+  ["12:34:56.987654321[UTC][foo=bar]", "with time zone"],
+  ["12:34:56.987654321[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["T12:34:56.987654321[foo=bar]", "with T"],
+  ["T12:34:56.987654321[UTC][foo=bar]", "with T and time zone"],
+  ["T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with T and calendar"],
+  ["T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with T, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar]", "with date"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar]", "with date and time zone"],
+  ["1970-01-01T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with date and calendar"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with date, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainDate(2000, 5, 2);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.toZonedDateTime({ plainTime: arg, timeZone: "UTC" });
+
+  assert.sameValue(
+    result.epochNanoseconds,
+    957_270_896_987_654_321n,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDate/prototype/until/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDate/prototype/until/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..221f1cf733e
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/until/argument-string-unknown-annotation.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.until
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainDate(2000, 5, 2);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.until(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDateTime/compare/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDateTime/compare/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..f4be81345ff
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/compare/argument-string-unknown-annotation.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.compare
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1976-11-18T15:23[foo=bar]", "alone"],
+  ["1976-11-18T15:23[UTC][foo=bar]", "with time zone"],
+  ["1976-11-18T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1976-11-18T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1976-11-18T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.PlainDateTime.compare(arg, arg);
+
+  assert.sameValue(
+    result,
+    0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDateTime/from/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDateTime/from/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..49b2dfc4336
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/from/argument-string-unknown-annotation.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.from
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["1976-11-18T15:23[foo=bar]", "alone"],
+  ["1976-11-18T15:23[UTC][foo=bar]", "with time zone"],
+  ["1976-11-18T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1976-11-18T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1976-11-18T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.PlainDateTime.from(arg);
+
+  TemporalHelpers.assertPlainDateTime(
+    result,
+    1976, 11, "M11", 18, 15, 23, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..eceefb2b92e
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-string-unknown-annotation.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.equals
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1976-11-18T15:23[foo=bar]", "alone"],
+  ["1976-11-18T15:23[UTC][foo=bar]", "with time zone"],
+  ["1976-11-18T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1976-11-18T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1976-11-18T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainDateTime(1976, 11, 18, 15, 23);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.equals(arg);
+
+  assert.sameValue(
+    result,
+    true,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..28220cd8e3d
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.since
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["1976-11-18T15:23[foo=bar]", "alone"],
+  ["1976-11-18T15:23[UTC][foo=bar]", "with time zone"],
+  ["1976-11-18T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1976-11-18T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1976-11-18T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainDateTime(1976, 11, 18, 15, 23);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.since(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..e5cb615127a
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.until
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["1976-11-18T15:23[foo=bar]", "alone"],
+  ["1976-11-18T15:23[UTC][foo=bar]", "with time zone"],
+  ["1976-11-18T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1976-11-18T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1976-11-18T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainDateTime(1976, 11, 18, 15, 23);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.until(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..1071909235b
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-string-unknown-annotation.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.withplaindate
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainDateTime(1976, 11, 18, 15, 23);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.withPlainDate(arg);
+
+  TemporalHelpers.assertPlainDateTime(
+    result,
+    2000, 5, "M05", 2, 15, 23, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withPlainTime/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainTime/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..307b1ba9ab9
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainTime/argument-string-unknown-annotation.js
@@ -0,0 +1,37 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.withplaintime
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["12:34:56.987654321[foo=bar]", "alone"],
+  ["12:34:56.987654321[UTC][foo=bar]", "with time zone"],
+  ["12:34:56.987654321[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["T12:34:56.987654321[foo=bar]", "with T"],
+  ["T12:34:56.987654321[UTC][foo=bar]", "with T and time zone"],
+  ["T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with T and calendar"],
+  ["T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with T, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar]", "with date"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar]", "with date and time zone"],
+  ["1970-01-01T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with date and calendar"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with date, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainDateTime(1976, 11, 18, 15, 23);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.withPlainTime(arg);
+
+  TemporalHelpers.assertPlainDateTime(
+    result,
+    1976, 11, "M11", 18, 12, 34, 56, 987, 654, 321,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainMonthDay/from/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainMonthDay/from/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..263377f4a36
--- /dev/null
+++ b/test/built-ins/Temporal/PlainMonthDay/from/argument-string-unknown-annotation.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainmonthday.from
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["1976-05-02T15:23[foo=bar]", "alone"],
+  ["1976-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["1976-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1976-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1976-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.PlainMonthDay.from(arg);
+
+  TemporalHelpers.assertPlainMonthDay(
+    result,
+    "M05", 2,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..bbed2a0c751
--- /dev/null
+++ b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-string-unknown-annotation.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainmonthday.prototype.equals
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1976-05-02T15:23[foo=bar]", "alone"],
+  ["1976-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["1976-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1976-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1976-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainMonthDay(5, 2);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.equals(arg);
+
+  assert.sameValue(
+    result,
+    true,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainTime/compare/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainTime/compare/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..0c7069446aa
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/compare/argument-string-unknown-annotation.js
@@ -0,0 +1,34 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.compare
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["12:34:56.987654321[foo=bar]", "alone"],
+  ["12:34:56.987654321[UTC][foo=bar]", "with time zone"],
+  ["12:34:56.987654321[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["T12:34:56.987654321[foo=bar]", "with T"],
+  ["T12:34:56.987654321[UTC][foo=bar]", "with T and time zone"],
+  ["T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with T and calendar"],
+  ["T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with T, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar]", "with date"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar]", "with date and time zone"],
+  ["1970-01-01T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with date and calendar"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with date, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.PlainTime.compare(arg, arg);
+
+  assert.sameValue(
+    result,
+    0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainTime/from/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainTime/from/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..9ef22988fb3
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/from/argument-string-unknown-annotation.js
@@ -0,0 +1,35 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.from
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["12:34:56.987654321[foo=bar]", "alone"],
+  ["12:34:56.987654321[UTC][foo=bar]", "with time zone"],
+  ["12:34:56.987654321[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["T12:34:56.987654321[foo=bar]", "with T"],
+  ["T12:34:56.987654321[UTC][foo=bar]", "with T and time zone"],
+  ["T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with T and calendar"],
+  ["T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with T, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar]", "with date"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar]", "with date and time zone"],
+  ["1970-01-01T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with date and calendar"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with date, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.PlainTime.from(arg);
+
+  TemporalHelpers.assertPlainTime(
+    result,
+    12, 34, 56, 987, 654, 321,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainTime/prototype/equals/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainTime/prototype/equals/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..4c4323d0695
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/equals/argument-string-unknown-annotation.js
@@ -0,0 +1,36 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.equals
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["12:34:56.987654321[foo=bar]", "alone"],
+  ["12:34:56.987654321[UTC][foo=bar]", "with time zone"],
+  ["12:34:56.987654321[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["T12:34:56.987654321[foo=bar]", "with T"],
+  ["T12:34:56.987654321[UTC][foo=bar]", "with T and time zone"],
+  ["T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with T and calendar"],
+  ["T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with T, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar]", "with date"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar]", "with date and time zone"],
+  ["1970-01-01T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with date and calendar"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with date, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainTime(12, 34, 56, 987, 654, 321);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.equals(arg);
+
+  assert.sameValue(
+    result,
+    true,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainTime/prototype/since/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainTime/prototype/since/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..8cf94c1edc5
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/since/argument-string-unknown-annotation.js
@@ -0,0 +1,37 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.since
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["12:34:56.987654321[foo=bar]", "alone"],
+  ["12:34:56.987654321[UTC][foo=bar]", "with time zone"],
+  ["12:34:56.987654321[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["T12:34:56.987654321[foo=bar]", "with T"],
+  ["T12:34:56.987654321[UTC][foo=bar]", "with T and time zone"],
+  ["T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with T and calendar"],
+  ["T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with T, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar]", "with date"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar]", "with date and time zone"],
+  ["1970-01-01T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with date and calendar"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with date, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainTime(12, 34, 56, 987, 654, 321);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.since(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainTime/prototype/toPlainDateTime/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainTime/prototype/toPlainDateTime/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..e8814197582
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/toPlainDateTime/argument-string-unknown-annotation.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.toplaindatetime
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainTime(12, 34, 56, 987, 654, 321);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.toPlainDateTime(arg);
+
+  TemporalHelpers.assertPlainDateTime(
+    result,
+    2000, 5, "M05", 2, 12, 34, 56, 987, 654, 321,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..2c829f70769
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.tozoneddatetime
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainTime(12, 34, 56, 987, 654, 321);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.toZonedDateTime({ plainDate: arg, timeZone: "UTC" });
+
+  assert.sameValue(
+    result.epochNanoseconds,
+    957_270_896_987_654_321n,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainTime/prototype/until/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainTime/prototype/until/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..2a6f5ff3cc0
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/until/argument-string-unknown-annotation.js
@@ -0,0 +1,37 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.until
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["12:34:56.987654321[foo=bar]", "alone"],
+  ["12:34:56.987654321[UTC][foo=bar]", "with time zone"],
+  ["12:34:56.987654321[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["T12:34:56.987654321[foo=bar]", "with T"],
+  ["T12:34:56.987654321[UTC][foo=bar]", "with T and time zone"],
+  ["T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with T and calendar"],
+  ["T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with T, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar]", "with date"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar]", "with date and time zone"],
+  ["1970-01-01T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with date and calendar"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with date, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainTime(12, 34, 56, 987, 654, 321);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.until(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainYearMonth/compare/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainYearMonth/compare/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..af273efc943
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/compare/argument-string-unknown-annotation.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.compare
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2019-12-15T15:23[foo=bar]", "alone"],
+  ["2019-12-15T15:23[UTC][foo=bar]", "with time zone"],
+  ["2019-12-15T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2019-12-15T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2019-12-15T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.PlainYearMonth.compare(arg, arg);
+
+  assert.sameValue(
+    result,
+    0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainYearMonth/from/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainYearMonth/from/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..7a1a5b915e7
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/from/argument-string-unknown-annotation.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.from
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["2019-12-15T15:23[foo=bar]", "alone"],
+  ["2019-12-15T15:23[UTC][foo=bar]", "with time zone"],
+  ["2019-12-15T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2019-12-15T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2019-12-15T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.PlainYearMonth.from(arg);
+
+  TemporalHelpers.assertPlainYearMonth(
+    result,
+    2019, 12, "M12",
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..7a6a52aa5a1
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-string-unknown-annotation.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.equals
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2019-12-15T15:23[foo=bar]", "alone"],
+  ["2019-12-15T15:23[UTC][foo=bar]", "with time zone"],
+  ["2019-12-15T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2019-12-15T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2019-12-15T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainYearMonth(2019, 12);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.equals(arg);
+
+  assert.sameValue(
+    result,
+    true,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..60870ca4827
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.since
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["2019-12-15T15:23[foo=bar]", "alone"],
+  ["2019-12-15T15:23[UTC][foo=bar]", "with time zone"],
+  ["2019-12-15T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2019-12-15T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2019-12-15T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainYearMonth(2019, 12);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.since(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-string-unknown-annotation.js b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..365c2bd84de
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.until
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["2019-12-15T15:23[foo=bar]", "alone"],
+  ["2019-12-15T15:23[UTC][foo=bar]", "with time zone"],
+  ["2019-12-15T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2019-12-15T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2019-12-15T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.PlainYearMonth(2019, 12);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.until(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getInstantFor/argument-string-unknown-annotation.js b/test/built-ins/Temporal/TimeZone/prototype/getInstantFor/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..91bb85df9f5
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getInstantFor/argument-string-unknown-annotation.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getinstantfor
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1976-11-18T15:23[foo=bar]", "alone"],
+  ["1976-11-18T15:23[UTC][foo=bar]", "with time zone"],
+  ["1976-11-18T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1976-11-18T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1976-11-18T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.TimeZone("UTC");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.getInstantFor(arg);
+
+  assert.sameValue(
+    result.epochNanoseconds,
+    217_178_580_000_000_000n,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getNextTransition/argument-string-unknown-annotation.js b/test/built-ins/Temporal/TimeZone/prototype/getNextTransition/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..53f49b74b99
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getNextTransition/argument-string-unknown-annotation.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getnexttransition
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00Z[foo=bar]", "alone"],
+  ["1970-01-01T00:00Z[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00Z[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1970-01-01T00:00Z[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1970-01-01T00:00Z[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.TimeZone("UTC");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.getNextTransition(arg);
+
+  assert.sameValue(
+    result,
+    null,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getOffsetNanosecondsFor/argument-string-unknown-annotation.js b/test/built-ins/Temporal/TimeZone/prototype/getOffsetNanosecondsFor/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..1534172c6ac
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getOffsetNanosecondsFor/argument-string-unknown-annotation.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getoffsetnanosecondsfor
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00Z[foo=bar]", "alone"],
+  ["1970-01-01T00:00Z[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00Z[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1970-01-01T00:00Z[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1970-01-01T00:00Z[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.TimeZone("UTC");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.getOffsetNanosecondsFor(arg);
+
+  assert.sameValue(
+    result,
+    0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getOffsetStringFor/argument-string-unknown-annotation.js b/test/built-ins/Temporal/TimeZone/prototype/getOffsetStringFor/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..46666bda446
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getOffsetStringFor/argument-string-unknown-annotation.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getoffsetstringfor
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00Z[foo=bar]", "alone"],
+  ["1970-01-01T00:00Z[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00Z[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1970-01-01T00:00Z[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1970-01-01T00:00Z[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.TimeZone("UTC");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.getOffsetStringFor(arg);
+
+  assert.sameValue(
+    result,
+    "+00:00",
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getPlainDateTimeFor/argument-string-unknown-annotation.js b/test/built-ins/Temporal/TimeZone/prototype/getPlainDateTimeFor/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..89983064f38
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getPlainDateTimeFor/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getplaindatetimefor
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00Z[foo=bar]", "alone"],
+  ["1970-01-01T00:00Z[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00Z[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1970-01-01T00:00Z[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1970-01-01T00:00Z[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.TimeZone("UTC");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.getPlainDateTimeFor(arg);
+
+  TemporalHelpers.assertPlainDateTime(
+    result,
+    1970, 1, "M01", 1, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getPossibleInstantsFor/argument-string-unknown-annotation.js b/test/built-ins/Temporal/TimeZone/prototype/getPossibleInstantsFor/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..dd94565cc5c
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getPossibleInstantsFor/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getpossibleinstantsfor
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [compareArray.js]
+---*/
+
+const tests = [
+  ["1976-11-18T15:23[foo=bar]", "alone"],
+  ["1976-11-18T15:23[UTC][foo=bar]", "with time zone"],
+  ["1976-11-18T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1976-11-18T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1976-11-18T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.TimeZone("UTC");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.getPossibleInstantsFor(arg);
+
+  assert.compareArray(
+    result.map(i => i.epochNanoseconds),
+    [217_178_580_000_000_000n],
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getPreviousTransition/argument-string-unknown-annotation.js b/test/built-ins/Temporal/TimeZone/prototype/getPreviousTransition/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..7d964fba19a
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getPreviousTransition/argument-string-unknown-annotation.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getprevioustransition
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00Z[foo=bar]", "alone"],
+  ["1970-01-01T00:00Z[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00Z[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["1970-01-01T00:00Z[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["1970-01-01T00:00Z[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.TimeZone("UTC");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.getPreviousTransition(arg);
+
+  assert.sameValue(
+    result,
+    null,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-string-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..8c9b5800814
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-string-unknown-annotation.js
@@ -0,0 +1,25 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.compare
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00[UTC][foo=bar][u-ca=iso8601]", "before calendar"],
+  ["1970-01-01T00:00[UTC][u-ca=iso8601][foo=bar]", "after calendar"],
+  ["1970-01-01T00:00[UTC][foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.ZonedDateTime.compare(arg, arg);
+
+  assert.sameValue(
+    result,
+    0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/argument-string-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/from/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..229abfa2205
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/from/argument-string-unknown-annotation.js
@@ -0,0 +1,25 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.from
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00[UTC][foo=bar][u-ca=iso8601]", "before calendar"],
+  ["1970-01-01T00:00[UTC][u-ca=iso8601][foo=bar]", "after calendar"],
+  ["1970-01-01T00:00[UTC][foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+tests.forEach(([arg, description]) => {
+  const result = Temporal.ZonedDateTime.from(arg);
+
+  assert.sameValue(
+    result.epochNanoseconds,
+    0n,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..eb815b4d71f
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-unknown-annotation.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.equals
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00[UTC][foo=bar][u-ca=iso8601]", "before calendar"],
+  ["1970-01-01T00:00[UTC][u-ca=iso8601][foo=bar]", "after calendar"],
+  ["1970-01-01T00:00[UTC][foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(0n, timeZone);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.equals(arg);
+
+  assert.sameValue(
+    result,
+    true,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..8e3b643be9c
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.since
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00[UTC][foo=bar][u-ca=iso8601]", "before calendar"],
+  ["1970-01-01T00:00[UTC][u-ca=iso8601][foo=bar]", "after calendar"],
+  ["1970-01-01T00:00[UTC][foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(0n, timeZone);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.since(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..471ef894156
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.until
+description: Various forms of unknown annotation
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const tests = [
+  ["1970-01-01T00:00[UTC][foo=bar]", "with time zone"],
+  ["1970-01-01T00:00[UTC][foo=bar][u-ca=iso8601]", "before calendar"],
+  ["1970-01-01T00:00[UTC][u-ca=iso8601][foo=bar]", "after calendar"],
+  ["1970-01-01T00:00[UTC][foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(0n, timeZone);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.until(arg);
+
+  TemporalHelpers.assertDuration(
+    result,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainDate/argument-string-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainDate/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..d07b5c627e5
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainDate/argument-string-unknown-annotation.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.withplaindate
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(0n, timeZone);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.withPlainDate(arg);
+
+  assert.sameValue(
+    result.epochNanoseconds,
+    957_225_600_000_000_000n,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-unknown-annotation.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..f5e4e9395c2
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/argument-string-unknown-annotation.js
@@ -0,0 +1,37 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.withplaintime
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["12:34:56.987654321[foo=bar]", "alone"],
+  ["12:34:56.987654321[UTC][foo=bar]", "with time zone"],
+  ["12:34:56.987654321[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["T12:34:56.987654321[foo=bar]", "with T"],
+  ["T12:34:56.987654321[UTC][foo=bar]", "with T and time zone"],
+  ["T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with T and calendar"],
+  ["T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with T, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar]", "with date"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar]", "with date and time zone"],
+  ["1970-01-01T12:34:56.987654321[u-ca=iso8601][foo=bar]", "with date and calendar"],
+  ["1970-01-01T12:34:56.987654321[UTC][foo=bar][u-ca=iso8601]", "with date, time zone, and calendar"],
+  ["1970-01-01T12:34:56.987654321[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(0n, timeZone);
+
+tests.forEach(([arg, description]) => {
+  const result = instance.withPlainTime(arg);
+
+  assert.sameValue(
+    result.epochNanoseconds,
+    45_296_987_654_321n,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/intl402/Temporal/Calendar/prototype/era/argument-string-unknown-annotation.js b/test/intl402/Temporal/Calendar/prototype/era/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..940ea78fa38
--- /dev/null
+++ b/test/intl402/Temporal/Calendar/prototype/era/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.era
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.era(arg);
+
+  assert.sameValue(
+    result,
+    undefined,
+    `unknown annotation (${description})`
+  );
+});
diff --git a/test/intl402/Temporal/Calendar/prototype/eraYear/argument-string-unknown-annotation.js b/test/intl402/Temporal/Calendar/prototype/eraYear/argument-string-unknown-annotation.js
new file mode 100644
index 00000000000..d98a8537b09
--- /dev/null
+++ b/test/intl402/Temporal/Calendar/prototype/eraYear/argument-string-unknown-annotation.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.erayear
+description: Various forms of unknown annotation
+features: [Temporal]
+---*/
+
+const tests = [
+  ["2000-05-02[foo=bar]", "without time"],
+  ["2000-05-02T15:23[foo=bar]", "alone"],
+  ["2000-05-02T15:23[UTC][foo=bar]", "with time zone"],
+  ["2000-05-02T15:23[u-ca=iso8601][foo=bar]", "with calendar"],
+  ["2000-05-02T15:23[UTC][foo=bar][u-ca=iso8601]", "with time zone and calendar"],
+  ["2000-05-02T15:23[foo=bar][_foo-bar0=Ignore-This-999999999999]", "with another unknown annotation"],
+];
+
+const instance = new Temporal.Calendar("iso8601");
+
+tests.forEach(([arg, description]) => {
+  const result = instance.eraYear(arg);
+
+  assert.sameValue(
+    result,
+    undefined,
+    `unknown annotation (${description})`
+  );
+});