diff --git a/test/built-ins/Temporal/Calendar/prototype/weekOfYear/custom-calendar-weekofyear.js b/test/built-ins/Temporal/Calendar/prototype/weekOfYear/custom-calendar-weekofyear.js
new file mode 100644
index 00000000000..c9871143617
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/weekOfYear/custom-calendar-weekofyear.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2024 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: >
+  Temporal.Calendar.prototype.weekOfYear returns undefined for all 
+  custom calendars where weekOfYear() returns undefined.
+features: [Temporal]
+---*/
+
+class CustomCalendar extends Temporal.Calendar {
+  constructor() {
+    super("iso8601");
+  }
+  weekOfYear() {
+    return undefined;
+  }
+}
+
+const calendar = new CustomCalendar();
+const customCalendarDate = { month: 1, day: 1, year: 2024, calendar};
+assert.sameValue(calendar.weekOfYear({...customCalendarDate}), undefined);
diff --git a/test/built-ins/Temporal/Calendar/prototype/yearOfWeek/custom-calendar-weekofyear.js b/test/built-ins/Temporal/Calendar/prototype/yearOfWeek/custom-calendar-weekofyear.js
new file mode 100644
index 00000000000..0440497eb9b
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/yearOfWeek/custom-calendar-weekofyear.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.yearofweek
+description: >
+  Temporal.Calendar.prototype.yearOfWeek returns undefined for all 
+  custom calendars where yearOfWeek() returns undefined.
+features: [Temporal]
+---*/
+
+class CustomCalendar extends Temporal.Calendar {
+  constructor() {
+    super("iso8601");
+  }
+  yearOfWeek() {
+    return undefined;
+  }
+}
+
+const calendar = new CustomCalendar();
+const customCalendarDate = { month: 1, day: 1, year: 2024, calendar};
+assert.sameValue(calendar.yearOfWeek({...customCalendarDate}), undefined);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/weekOfYear/custom-calendar-weekofyear.js b/test/built-ins/Temporal/PlainDate/prototype/weekOfYear/custom-calendar-weekofyear.js
new file mode 100644
index 00000000000..35261207ed9
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/weekOfYear/custom-calendar-weekofyear.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.weekofyear
+description: >
+  Temporal.PlainDate.prototype.weekOfYear returns undefined for all 
+  custom calendars where weekOfYear() returns undefined.
+features: [Temporal]
+---*/
+
+class CustomCalendar extends Temporal.Calendar {
+  constructor() {
+    super("iso8601");
+  }
+  weekOfYear() {
+    return undefined;
+  }
+}
+
+const calendar = new CustomCalendar();
+const customCalendarDate = new Temporal.PlainDate(2024, 1, 1, calendar);
+assert.sameValue(customCalendarDate.weekOfYear, undefined);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/yearOfWeek/custom-calendar-weekofyear.js b/test/built-ins/Temporal/PlainDate/prototype/yearOfWeek/custom-calendar-weekofyear.js
new file mode 100644
index 00000000000..fdb51a1b172
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/yearOfWeek/custom-calendar-weekofyear.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.yearofweek
+description: >
+  Temporal.PlainDate.prototype.yearOfWeek returns undefined for all 
+  custom calendars where yearOfWeek() returns undefined.
+features: [Temporal]
+---*/
+
+class CustomCalendar extends Temporal.Calendar {
+  constructor() {
+    super("iso8601");
+  }
+  yearOfWeek() {
+    return undefined;
+  }
+}
+
+const calendar = new CustomCalendar();
+const customCalendarDate = new Temporal.PlainDate(2024, 1, 1, calendar);
+assert.sameValue(customCalendarDate.yearOfWeek, undefined);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/weekOfYear/custom-calendar-weekofyear.js b/test/built-ins/Temporal/PlainDateTime/prototype/weekOfYear/custom-calendar-weekofyear.js
new file mode 100644
index 00000000000..f9b43f88afe
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/weekOfYear/custom-calendar-weekofyear.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.weekofyear
+description: >
+  Temporal.PlainDateTime.prototype.weekOfYear returns undefined for all 
+  custom calendars where weekOfYear() returns undefined.
+features: [Temporal]
+---*/
+
+class CustomCalendar extends Temporal.Calendar {
+  constructor() {
+    super("iso8601");
+  }
+  weekOfYear() {
+    return undefined;
+  }
+}
+
+const calendar = new CustomCalendar();
+const customCalendarDate = new Temporal.PlainDateTime(2024, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
+assert.sameValue(customCalendarDate.weekOfYear, undefined);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/yearOfWeek/custom-calendar-weekofyear.js b/test/built-ins/Temporal/PlainDateTime/prototype/yearOfWeek/custom-calendar-weekofyear.js
new file mode 100644
index 00000000000..425b3a0360b
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/yearOfWeek/custom-calendar-weekofyear.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.yearofweek
+description: >
+  Temporal.PlainDateTime.prototype.yearOfWeek returns undefined for all 
+  custom calendars where yearOfWeek() returns undefined.
+features: [Temporal]
+---*/
+
+class CustomCalendar extends Temporal.Calendar {
+  constructor() {
+    super("iso8601");
+  }
+  yearOfWeek() {
+    return undefined;
+  }
+}
+
+const calendar = new CustomCalendar();
+const customCalendarDate = new Temporal.PlainDateTime(2024, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
+assert.sameValue(customCalendarDate.yearOfWeek, undefined);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/weekOfYear/custom-calendar-weekofyear.js b/test/built-ins/Temporal/ZonedDateTime/prototype/weekOfYear/custom-calendar-weekofyear.js
new file mode 100644
index 00000000000..ed8df20d109
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/weekOfYear/custom-calendar-weekofyear.js
@@ -0,0 +1,24 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.weekofyear
+description: >
+  Temporal.ZonedDateTime.prototype.weekOfYear returns undefined for all 
+  custom calendars where weekOfYear() returns undefined.
+features: [Temporal]
+---*/
+
+class CustomCalendar extends Temporal.Calendar {
+  constructor() {
+    super("iso8601");
+  }
+  weekOfYear() {
+    return undefined;
+  }
+}
+
+const calendar = new CustomCalendar();
+// Epoch Nanoseconds for new Temporal.PlainDateTime(2024, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
+const customCalendarDate = new Temporal.ZonedDateTime(1_704_112_496_987_654_321n, "UTC", calendar);
+assert.sameValue(customCalendarDate.weekOfYear, undefined);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/yearOfWeek/custom-calendar-weekofyear.js b/test/built-ins/Temporal/ZonedDateTime/prototype/yearOfWeek/custom-calendar-weekofyear.js
new file mode 100644
index 00000000000..0c5c3723c79
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/yearOfWeek/custom-calendar-weekofyear.js
@@ -0,0 +1,24 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.yearofweek
+description: >
+  Temporal.ZonedDateTime.prototype.yearOfWeek returns undefined for all 
+  custom calendars where yearOfWeek() returns undefined.
+features: [Temporal]
+---*/
+
+class CustomCalendar extends Temporal.Calendar {
+  constructor() {
+    super("iso8601");
+  }
+  yearOfWeek() {
+    return undefined;
+  }
+}
+
+const calendar = new CustomCalendar();
+// Epoch Nanoseconds for new Temporal.PlainDateTime(2024, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
+const customCalendarDate = new Temporal.ZonedDateTime(1_704_112_496_987_654_321n, "UTC", calendar);
+assert.sameValue(customCalendarDate.yearOfWeek, undefined);
diff --git a/test/intl402/Temporal/Calendar/prototype/weekOfYear/gregory-iso-weekofyear.js b/test/intl402/Temporal/Calendar/prototype/weekOfYear/gregory-iso-weekofyear.js
new file mode 100644
index 00000000000..1b2d2d3d4b9
--- /dev/null
+++ b/test/intl402/Temporal/Calendar/prototype/weekOfYear/gregory-iso-weekofyear.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2024 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: >
+  In the ISO 8601 week calendar, calendar week number 1 of a calendar year is 
+  the week including the first Thursday of that year (based on the principle 
+  that a week belongs to the same calendar year as the majority of its calendar 
+  days). Because of this, some calendar days of the first calendar week of a 
+  calendar year may be part of the preceding date calendar year, and some 
+  calendar days of the last calendar week of a calendar year may be part of
+  the next calendar year.
+features: [Temporal]
+---*/
+
+// 
+
+let calendar = new Temporal.Calendar("gregory");
+const date = { month: 1, day: 1, year: 2021, calendar};
+
+assert.sameValue(calendar.weekOfYear({...date}), 1);
+
+calendar = new Temporal.Calendar("iso8601");
+const isodate = { month: 1, day: 1, year: 2021, calendar};
+
+assert.sameValue(calendar.weekOfYear({...isodate}), 53);
diff --git a/test/intl402/Temporal/Calendar/prototype/yearOfWeek/gregory-iso-weekofyear.js b/test/intl402/Temporal/Calendar/prototype/yearOfWeek/gregory-iso-weekofyear.js
new file mode 100644
index 00000000000..65f73d7a2bc
--- /dev/null
+++ b/test/intl402/Temporal/Calendar/prototype/yearOfWeek/gregory-iso-weekofyear.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.yearofweek
+description: >
+  In the ISO 8601 week calendar, calendar week number 1 of a calendar year is 
+  the week including the first Thursday of that year (based on the principle 
+  that a week belongs to the same calendar year as the majority of its calendar 
+  days). Because of this, some calendar days of the first calendar week of a 
+  calendar year may be part of the preceding date calendar year, and some 
+  calendar days of the last calendar week of a calendar year may be part of
+  the next calendar year.
+features: [Temporal]
+---*/
+
+// 
+
+let calendar = new Temporal.Calendar("gregory");
+const date = { month: 1, day: 1, year: 2021, calendar};
+
+assert.sameValue(calendar.yearOfWeek({...date}), 2021);
+
+calendar = new Temporal.Calendar("iso8601");
+const isodate = { month: 1, day: 1, year: 2021, calendar};
+
+assert.sameValue(calendar.yearOfWeek({...isodate}), 2020);
diff --git a/test/intl402/Temporal/PlainDate/prototype/weekOfYear/gregory-iso-weekofyear.js b/test/intl402/Temporal/PlainDate/prototype/weekOfYear/gregory-iso-weekofyear.js
new file mode 100644
index 00000000000..4d023823352
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/weekOfYear/gregory-iso-weekofyear.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.weekofyear
+description: >
+  In the ISO 8601 week calendar, calendar week number 1 of a calendar year is 
+  the week including the first Thursday of that year (based on the principle 
+  that a week belongs to the same calendar year as the majority of its calendar 
+  days). Because of this, some calendar days of the first calendar week of a 
+  calendar year may be part of the preceding date calendar year, and some 
+  calendar days of the last calendar week of a calendar year may be part of
+  the next calendar year.
+features: [Temporal]
+---*/
+
+// 
+
+let calendar = new Temporal.Calendar("gregory");
+const date = new Temporal.PlainDate(2021, 1, 1, calendar);
+
+assert.sameValue(date.weekOfYear, 1);
+
+calendar = new Temporal.Calendar("iso8601");
+const isodate = new Temporal.PlainDate(2021, 1, 1, calendar);
+
+assert.sameValue(isodate.weekOfYear, 53);
diff --git a/test/intl402/Temporal/PlainDate/prototype/yearOfWeek/gregory-iso-weekofyear.js b/test/intl402/Temporal/PlainDate/prototype/yearOfWeek/gregory-iso-weekofyear.js
new file mode 100644
index 00000000000..70252942e90
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/yearOfWeek/gregory-iso-weekofyear.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.yearofweek
+description: >
+  In the ISO 8601 week calendar, calendar week number 1 of a calendar year is 
+  the week including the first Thursday of that year (based on the principle 
+  that a week belongs to the same calendar year as the majority of its calendar 
+  days). Because of this, some calendar days of the first calendar week of a 
+  calendar year may be part of the preceding date calendar year, and some 
+  calendar days of the last calendar week of a calendar year may be part of
+  the next calendar year.
+features: [Temporal]
+---*/
+
+// 
+
+let calendar = new Temporal.Calendar("gregory");
+const date = new Temporal.PlainDate(2021, 1, 1, calendar);
+
+assert.sameValue(date.yearOfWeek, 2021);
+
+calendar = new Temporal.Calendar("iso8601");
+const isodate = new Temporal.PlainDate(2021, 1, 1, calendar);
+
+assert.sameValue(isodate.yearOfWeek, 2020);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js b/test/intl402/Temporal/PlainDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js
new file mode 100644
index 00000000000..6f79fd1c117
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.weekofyear
+description: >
+  In the ISO 8601 week calendar, calendar week number 1 of a calendar year is 
+  the week including the first Thursday of that year (based on the principle 
+  that a week belongs to the same calendar year as the majority of its calendar 
+  days). Because of this, some calendar days of the first calendar week of a 
+  calendar year may be part of the preceding date calendar year, and some 
+  calendar days of the last calendar week of a calendar year may be part of
+  the next calendar year.
+features: [Temporal]
+---*/
+
+// 
+
+let calendar = new Temporal.Calendar("gregory");
+const date = new Temporal.PlainDateTime(2021, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
+
+assert.sameValue(date.weekOfYear, 1);
+
+calendar = new Temporal.Calendar("iso8601");
+const isodate = new Temporal.PlainDateTime(2021, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
+
+assert.sameValue(isodate.weekOfYear, 53);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js b/test/intl402/Temporal/PlainDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js
new file mode 100644
index 00000000000..63bd715a1b2
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.yearofweek
+description: >
+  In the ISO 8601 week calendar, calendar week number 1 of a calendar year is 
+  the week including the first Thursday of that year (based on the principle 
+  that a week belongs to the same calendar year as the majority of its calendar 
+  days). Because of this, some calendar days of the first calendar week of a 
+  calendar year may be part of the preceding date calendar year, and some 
+  calendar days of the last calendar week of a calendar year may be part of
+  the next calendar year.
+features: [Temporal]
+---*/
+
+// 
+
+let calendar = new Temporal.Calendar("gregory");
+const date = new Temporal.PlainDateTime(2021, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
+
+assert.sameValue(date.yearOfWeek, 2021);
+
+calendar = new Temporal.Calendar("iso8601");
+const isodate = new Temporal.PlainDateTime(2021, 1, 1, 12, 34, 56, 987, 654, 321, calendar);
+
+assert.sameValue(isodate.yearOfWeek, 2020);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js b/test/intl402/Temporal/ZonedDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js
new file mode 100644
index 00000000000..c02e49a0b4d
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/weekOfYear/gregory-iso-weekofyear.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.weekofyear
+description: >
+  In the ISO 8601 week calendar, calendar week number 1 of a calendar year is 
+  the week including the first Thursday of that year (based on the principle 
+  that a week belongs to the same calendar year as the majority of its calendar 
+  days). Because of this, some calendar days of the first calendar week of a 
+  calendar year may be part of the preceding date calendar year, and some 
+  calendar days of the last calendar week of a calendar year may be part of
+  the next calendar year.
+features: [Temporal]
+---*/
+
+// 
+
+let calendar = new Temporal.Calendar("gregory");
+const date = new Temporal.ZonedDateTime(1_609_504_496_987_654_321n, "UTC", calendar);
+
+assert.sameValue(date.weekOfYear, 1);
+
+calendar = new Temporal.Calendar("iso8601");
+const isodate = new Temporal.ZonedDateTime(1_609_504_496_987_654_321n, "UTC", calendar);
+
+assert.sameValue(isodate.weekOfYear, 53);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js b/test/intl402/Temporal/ZonedDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js
new file mode 100644
index 00000000000..439a5173d11
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/yearOfWeek/gregory-iso-weekofyear.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.yearofweek
+description: >
+  In the ISO 8601 week calendar, calendar week number 1 of a calendar year is 
+  the week including the first Thursday of that year (based on the principle 
+  that a week belongs to the same calendar year as the majority of its calendar 
+  days). Because of this, some calendar days of the first calendar week of a 
+  calendar year may be part of the preceding date calendar year, and some 
+  calendar days of the last calendar week of a calendar year may be part of
+  the next calendar year.
+features: [Temporal]
+---*/
+
+// 
+
+let calendar = new Temporal.Calendar("gregory");
+const date = new Temporal.ZonedDateTime(1_609_504_496_987_654_321n, "UTC", calendar);
+
+assert.sameValue(date.yearOfWeek, 2021);
+
+calendar = new Temporal.Calendar("iso8601");
+const isodate = new Temporal.ZonedDateTime(1_609_504_496_987_654_321n, "UTC", calendar);
+
+assert.sameValue(isodate.yearOfWeek, 2020);