diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3bfbf669f..6124b6a3a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 [Full changelog](https://github.com/mozilla/glean.js/compare/v0.10.2...main)
 
 * [#202](https://github.com/mozilla/glean.js/pull/202): Add a testing API for the ping type.
+* [#253](https://github.com/mozilla/glean.js/pull/253): Implement the timespan metric type.
 
 # v0.10.2 (2021-04-26)
 
diff --git a/glean/src/core/glean.ts b/glean/src/core/glean.ts
index 763ead6c3..e7bbb18c9 100644
--- a/glean/src/core/glean.ts
+++ b/glean/src/core/glean.ts
@@ -12,8 +12,7 @@ import { isUndefined, sanitizeApplicationId } from "./utils.js";
 import { CoreMetrics } from "./internal_metrics.js";
 import EventsDatabase from "./metrics/events_database.js";
 import UUIDMetricType from "./metrics/types/uuid.js";
-import DatetimeMetricType from "./metrics/types/datetime.js";
-import { DatetimeMetric } from "./metrics/types/datetime_metric.js";
+import DatetimeMetricType, { DatetimeMetric } from "./metrics/types/datetime.js";
 import CorePings from "./internal_pings.js";
 import { registerPluginToEvent, testResetEvents } from "./events/utils.js";
 
diff --git a/glean/src/core/metrics/database.ts b/glean/src/core/metrics/database.ts
index 1767a496c..38ebdc718 100644
--- a/glean/src/core/metrics/database.ts
+++ b/glean/src/core/metrics/database.ts
@@ -5,11 +5,11 @@
 import type Store from "../storage/index.js";
 import type { MetricType } from "./index.js";
 import type { Metric } from "./metric.js";
-import { createMetric, validateMetricInternalRepresentation } from "./utils.js";
+import type { StorageBuilder } from "../../platform/index.js";
+import type { Metrics } from "./index.js";
 import type { JSONObject, JSONValue } from "../utils.js";
+import { createMetric, validateMetricInternalRepresentation } from "./utils.js";
 import { isObject, isUndefined } from "../utils.js";
-import type { StorageBuilder } from "../../platform/index.js";
-import type { Metrics } from "./metrics_interface";
 import { Lifetime } from "./lifetime.js";
 
 /**
diff --git a/glean/src/core/metrics/index.ts b/glean/src/core/metrics/index.ts
index 3ce2dc7e2..78eafa846 100644
--- a/glean/src/core/metrics/index.ts
+++ b/glean/src/core/metrics/index.ts
@@ -3,11 +3,17 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 import type { JSONValue } from "../utils.js";
-import { isUndefined } from "../utils.js";
-import { Metric } from "./metric.js";
 import type { Lifetime } from "./lifetime.js";
 import type MetricsDatabase from "./database.js";
-import { getValidDynamicLabel } from "./types/labeled_utils.js";
+import { isUndefined } from "../utils.js";
+import { getValidDynamicLabel } from "./types/labeled.js";
+
+export interface Metrics {
+  [aMetricType: string]: {
+    [aMetricIdentifier: string]: JSONValue;
+  };
+}
+
 
 /**
  * The common set of data shared across all different metric types.
@@ -103,27 +109,3 @@ export abstract class MetricType implements CommonMetricData {
     return (uploadEnabled && !this.disabled);
   }
 }
-
-/**
- * This is an internal metric representation for labeled metrics.
- *
- * This can be used to instruct the validators to simply report
- * whatever is stored internally, without performing any specific
- * validation.
- *
- * This needs to live here, instead of labeled.ts, in order to avoid
- * a cyclic dependency.
- */
-export class LabeledMetric extends Metric<JSONValue, JSONValue> {
-  constructor(v: unknown) {
-    super(v);
-  }
-
-  validate(v: unknown): v is JSONValue {
-    return true;
-  }
-
-  payload(): JSONValue {
-    return this._inner;
-  }
-}
diff --git a/glean/src/core/metrics/metrics_interface.ts b/glean/src/core/metrics/metrics_interface.ts
deleted file mode 100644
index e52e88ebe..000000000
--- a/glean/src/core/metrics/metrics_interface.ts
+++ /dev/null
@@ -1,11 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-import type { JSONValue } from "../utils.js";
-
-export interface Metrics {
-  [aMetricType: string]: {
-    [aMetricIdentifier: string]: JSONValue;
-  };
-}
diff --git a/glean/src/core/metrics/types/boolean.ts b/glean/src/core/metrics/types/boolean.ts
index 071848bc7..20597b199 100644
--- a/glean/src/core/metrics/types/boolean.ts
+++ b/glean/src/core/metrics/types/boolean.ts
@@ -4,8 +4,23 @@
 
 import type { CommonMetricData } from "../index.js";
 import { MetricType } from "../index.js";
-import { BooleanMetric } from "./boolean_metric.js";
 import { Context } from "../../context.js";
+import { Metric } from "../metric.js";
+import { isBoolean } from "../../utils.js";
+
+export class BooleanMetric extends Metric<boolean, boolean> {
+  constructor(v: unknown) {
+    super(v);
+  }
+
+  validate(v: unknown): v is boolean {
+    return isBoolean(v);
+  }
+  payload(): boolean {
+    return this._inner;
+  }
+}
+
 
 /**
  *  A boolean metric.
diff --git a/glean/src/core/metrics/types/boolean_metric.ts b/glean/src/core/metrics/types/boolean_metric.ts
deleted file mode 100644
index f2bf3e03e..000000000
--- a/glean/src/core/metrics/types/boolean_metric.ts
+++ /dev/null
@@ -1,19 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-import { Metric } from "../metric.js";
-import { isBoolean } from "../../utils.js";
-
-export class BooleanMetric extends Metric<boolean, boolean> {
-  constructor(v: unknown) {
-    super(v);
-  }
-
-  validate(v: unknown): v is boolean {
-    return isBoolean(v);
-  }
-  payload(): boolean {
-    return this._inner;
-  }
-}
diff --git a/glean/src/core/metrics/types/counter.ts b/glean/src/core/metrics/types/counter.ts
index e9b099955..a2644b9ba 100644
--- a/glean/src/core/metrics/types/counter.ts
+++ b/glean/src/core/metrics/types/counter.ts
@@ -3,11 +3,33 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 import type { CommonMetricData } from "../index.js";
-import { MetricType } from "../index.js";
 import type { JSONValue } from "../../utils.js";
-import { isUndefined } from "../../utils.js";
-import { CounterMetric } from "./counter_metric.js";
+import { MetricType } from "../index.js";
+import { isUndefined, isNumber } from "../../utils.js";
 import { Context } from "../../context.js";
+import { Metric } from "../metric.js";
+
+export class CounterMetric extends Metric<number, number> {
+  constructor(v: unknown) {
+    super(v);
+  }
+
+  validate(v: unknown): v is number {
+    if (!isNumber(v)) {
+      return false;
+    }
+
+    if (v <= 0) {
+      return false;
+    }
+
+    return true;
+  }
+
+  payload(): number {
+    return this._inner;
+  }
+}
 
 /**
  * A counter metric.
diff --git a/glean/src/core/metrics/types/counter_metric.ts b/glean/src/core/metrics/types/counter_metric.ts
deleted file mode 100644
index 368a343d3..000000000
--- a/glean/src/core/metrics/types/counter_metric.ts
+++ /dev/null
@@ -1,28 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-import { Metric } from "../metric.js";
-import { isNumber } from "../../utils.js";
-
-export class CounterMetric extends Metric<number, number> {
-  constructor(v: unknown) {
-    super(v);
-  }
-
-  validate(v: unknown): v is number {
-    if (!isNumber(v)) {
-      return false;
-    }
-
-    if (v <= 0) {
-      return false;
-    }
-
-    return true;
-  }
-
-  payload(): number {
-    return this._inner;
-  }
-}
diff --git a/glean/src/core/metrics/types/datetime.ts b/glean/src/core/metrics/types/datetime.ts
index 5f03d842a..02e75f904 100644
--- a/glean/src/core/metrics/types/datetime.ts
+++ b/glean/src/core/metrics/types/datetime.ts
@@ -5,9 +5,157 @@
 import type { CommonMetricData } from "../index.js";
 import { MetricType } from "../index.js";
 import TimeUnit from "../../metrics/time_unit.js";
-import type { DatetimeInternalRepresentation} from "./datetime_metric.js";
-import { DatetimeMetric } from "./datetime_metric.js";
 import { Context } from "../../context.js";
+import { Metric } from "../metric.js";
+import { isNumber, isObject, isString } from "../../utils.js";
+
+/**
+ * Builds the formatted timezone offset string frim a given timezone.
+ *
+ * The format of the resulting string is `+02:00`.
+ *
+ * @param timezone A number representing the timezone offset to format,
+ *                 this is expected to be in minutes.
+ *
+ * @returns The formatted timezone offset string.
+ */
+export function formatTimezoneOffset(timezone: number): string {
+  const offset = (timezone / 60) * -1;
+  const sign = offset > 0 ? "+" : "-";
+  const hours = Math.abs(offset).toString().padStart(2, "0");
+  return `${sign}${hours}:00`;
+}
+
+export type DatetimeInternalRepresentation = {
+  // The time unit of the metric type at the time of recording.
+  timeUnit: TimeUnit,
+  // This timezone should be the exact output of `Date.getTimezoneOffset`
+  // and as such it should alwaye be in minutes.
+  timezone: number,
+  // This date string should be the exact output of `Date.toISOString`
+  // and as such it is always in UTC.
+  date: string,
+};
+
+export class DatetimeMetric extends Metric<DatetimeInternalRepresentation, string> {
+  constructor(v: unknown) {
+    super(v);
+  }
+
+  static fromDate(v: Date, timeUnit: TimeUnit): DatetimeMetric {
+    return new DatetimeMetric({
+      timeUnit,
+      timezone: v.getTimezoneOffset(),
+      date: v.toISOString()
+    });
+  }
+
+  /**
+   * Gets the datetime data as a Date object.
+   *
+   * # Note
+   *
+   * The object created here will be relative to local time.
+   * If the timezone at the time of recording is different,
+   * the timezone offset will be applied before transforming to an object.
+   *
+   * @returns A date object.
+   */
+  get date(): Date {
+    return new Date(this._inner.date);
+  }
+
+  private get timezone(): number {
+    return this._inner.timezone;
+  }
+
+  private get timeUnit(): TimeUnit {
+    return this._inner.timeUnit;
+  }
+
+  private get dateISOString(): string {
+    return this._inner.date;
+  }
+
+  validate(v: unknown): v is DatetimeInternalRepresentation {
+    if (!isObject(v) || Object.keys(v).length !== 3) {
+      return false;
+    }
+
+    const timeUnitVerification = "timeUnit" in v && isString(v.timeUnit) && Object.values(TimeUnit).includes(v.timeUnit as TimeUnit);
+    const timezoneVerification = "timezone" in v && isNumber(v.timezone);
+    const dateVerification = "date" in v && isString(v.date) && v.date.length === 24 && !isNaN(Date.parse(v.date));
+    if (!timeUnitVerification || !timezoneVerification || !dateVerification) {
+      return false;
+    }
+
+    return true;
+  }
+
+  /**
+   * Gets this metrics value in its payload representation.
+   *
+   * For this metric, the payload is the timezone aware ISO date string truncated to the time unit
+   * given at the time of recording.
+   *
+   * # Note
+   *
+   * The timezone of the final string is the timezone at the time of recording.
+   *
+   * @returns The metric value.
+   */
+  payload(): string {
+    const extractedDateInfo = this.dateISOString.match(/\d+/g);
+    if (!extractedDateInfo || extractedDateInfo.length < 0) {
+      // This is impossible because the date is always validated before setting
+      throw new Error("IMPOSSIBLE: Unable to extract date information from DatetimeMetric.");
+    }
+    const correctedDate = new Date(
+      /* year */ parseInt(extractedDateInfo[0]),
+      /* month */ parseInt(extractedDateInfo[1]) - 1,
+      /* day */ parseInt(extractedDateInfo[2]),
+      /* hour */ parseInt(extractedDateInfo[3]) - (this.timezone / 60),
+      /* minute */ parseInt(extractedDateInfo[4]),
+      /* second */ parseInt(extractedDateInfo[5]),
+      /* millisecond */ parseInt(extractedDateInfo[6])
+    );
+
+    const timezone = formatTimezoneOffset(this.timezone);
+    const year = correctedDate.getFullYear().toString().padStart(2, "0");
+    // `Date.prototype.getMonth` returns the month starting at 0.
+    const month = (correctedDate.getMonth() + 1).toString().padStart(2, "0");
+    const day = correctedDate.getDate().toString().padStart(2, "0");
+    if (this.timeUnit === TimeUnit.Day) {
+      return `${year}-${month}-${day}${timezone}`;
+    }
+
+    const hours = correctedDate.getHours().toString().padStart(2, "0");
+    if (this.timeUnit === TimeUnit.Hour) {
+      return `${year}-${month}-${day}T${hours}${timezone}`;
+    }
+
+    const minutes = correctedDate.getMinutes().toString().padStart(2, "0");
+    if (this.timeUnit === TimeUnit.Minute) {
+      return `${year}-${month}-${day}T${hours}:${minutes}${timezone}`;
+    }
+
+    const seconds = correctedDate.getSeconds().toString().padStart(2, "0");
+    if (this.timeUnit === TimeUnit.Second) {
+      return `${year}-${month}-${day}T${hours}:${minutes}:${seconds}${timezone}`;
+    }
+
+    const milliseconds = correctedDate.getMilliseconds().toString().padStart(3, "0");
+    if (this.timeUnit === TimeUnit.Millisecond) {
+      return `${year}-${month}-${day}T${hours}:${minutes}:${seconds}.${milliseconds}${timezone}`;
+    }
+
+    if (this.timeUnit === TimeUnit.Microsecond) {
+      return `${year}-${month}-${day}T${hours}:${minutes}:${seconds}.${milliseconds}000${timezone}`;
+    }
+
+    return `${year}-${month}-${day}T${hours}:${minutes}:${seconds}.${milliseconds}000000${timezone}`;
+  }
+}
 
 /**
  * A datetime metric.
diff --git a/glean/src/core/metrics/types/datetime_metric.ts b/glean/src/core/metrics/types/datetime_metric.ts
deleted file mode 100644
index 22b74f8f0..000000000
--- a/glean/src/core/metrics/types/datetime_metric.ts
+++ /dev/null
@@ -1,155 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-import { Metric } from "../metric.js";
-import TimeUnit from "../time_unit.js";
-import { isNumber, isObject, isString } from "../../utils.js";
-
-/**
- * Builds the formatted timezone offset string frim a given timezone.
- *
- * The format of the resulting string is `+02:00`.
- *
- * @param timezone A number representing the timezone offset to format,
- *                 this is expected to be in minutes.
- *
- * @returns The formatted timezone offset string.
- */
-export function formatTimezoneOffset(timezone: number): string {
-  const offset = (timezone / 60) * -1;
-  const sign = offset > 0 ? "+" : "-";
-  const hours = Math.abs(offset).toString().padStart(2, "0");
-  return `${sign}${hours}:00`;
-}
-
-export type DatetimeInternalRepresentation = {
-  // The time unit of the metric type at the time of recording.
-  timeUnit: TimeUnit,
-  // This timezone should be the exact output of `Date.getTimezoneOffset`
-  // and as such it should alwaye be in minutes.
-  timezone: number,
-  // This date string should be the exact output of `Date.toISOString`
-  // and as such it is always in UTC.
-  date: string,
-};
-
-export class DatetimeMetric extends Metric<DatetimeInternalRepresentation, string> {
-  constructor(v: unknown) {
-    super(v);
-  }
-
-  static fromDate(v: Date, timeUnit: TimeUnit): DatetimeMetric {
-    return new DatetimeMetric({
-      timeUnit,
-      timezone: v.getTimezoneOffset(),
-      date: v.toISOString()
-    });
-  }
-
-  /**
-   * Gets the datetime data as a Date object.
-   *
-   * # Note
-   *
-   * The object created here will be relative to local time.
-   * If the timezone at the time of recording is different,
-   * the timezone offset will be applied before transforming to an object.
-   *
-   * @returns A date object.
-   */
-  get date(): Date {
-    return new Date(this._inner.date);
-  }
-
-  private get timezone(): number {
-    return this._inner.timezone;
-  }
-
-  private get timeUnit(): TimeUnit {
-    return this._inner.timeUnit;
-  }
-
-  private get dateISOString(): string {
-    return this._inner.date;
-  }
-
-  validate(v: unknown): v is DatetimeInternalRepresentation {
-    if (!isObject(v) || Object.keys(v).length !== 3) {
-      return false;
-    }
-
-    const timeUnitVerification = "timeUnit" in v && isString(v.timeUnit) && Object.values(TimeUnit).includes(v.timeUnit as TimeUnit);
-    const timezoneVerification = "timezone" in v && isNumber(v.timezone);
-    const dateVerification = "date" in v && isString(v.date) && v.date.length === 24 && !isNaN(Date.parse(v.date));
-    if (!timeUnitVerification || !timezoneVerification || !dateVerification) {
-      return false;
-    }
-
-    return true;
-  }
-
-  /**
-   * Gets this metrics value in its payload representation.
-   *
-   * For this metric, the payload is the timezone aware ISO date string truncated to the time unit
-   * given at the time of recording.
-   *
-   * # Note
-   *
-   * The timezone of the final string is the timezone at the time of recording.
-   *
-   * @returns The metric value.
-   */
-  payload(): string {
-    const extractedDateInfo = this.dateISOString.match(/\d+/g);
-    if (!extractedDateInfo || extractedDateInfo.length < 0) {
-      // This is impossible because the date is always validated before setting
-      throw new Error("IMPOSSIBLE: Unable to extract date information from DatetimeMetric.");
-    }
-    const correctedDate = new Date(
-      /* year */ parseInt(extractedDateInfo[0]),
-      /* month */ parseInt(extractedDateInfo[1]) - 1,
-      /* day */ parseInt(extractedDateInfo[2]),
-      /* hour */ parseInt(extractedDateInfo[3]) - (this.timezone / 60),
-      /* minute */ parseInt(extractedDateInfo[4]),
-      /* second */ parseInt(extractedDateInfo[5]),
-      /* millisecond */ parseInt(extractedDateInfo[6])
-    );
-
-    const timezone = formatTimezoneOffset(this.timezone);
-    const year = correctedDate.getFullYear().toString().padStart(2, "0");
-    // `Date.prototype.getMonth` returns the month starting at 0.
-    const month = (correctedDate.getMonth() + 1).toString().padStart(2, "0");
-    const day = correctedDate.getDate().toString().padStart(2, "0");
-    if (this.timeUnit === TimeUnit.Day) {
-      return `${year}-${month}-${day}${timezone}`;
-    }
-
-    const hours = correctedDate.getHours().toString().padStart(2, "0");
-    if (this.timeUnit === TimeUnit.Hour) {
-      return `${year}-${month}-${day}T${hours}${timezone}`;
-    }
-
-    const minutes = correctedDate.getMinutes().toString().padStart(2, "0");
-    if (this.timeUnit === TimeUnit.Minute) {
-      return `${year}-${month}-${day}T${hours}:${minutes}${timezone}`;
-    }
-
-    const seconds = correctedDate.getSeconds().toString().padStart(2, "0");
-    if (this.timeUnit === TimeUnit.Second) {
-      return `${year}-${month}-${day}T${hours}:${minutes}:${seconds}${timezone}`;
-    }
-
-    const milliseconds = correctedDate.getMilliseconds().toString().padStart(3, "0");
-    if (this.timeUnit === TimeUnit.Millisecond) {
-      return `${year}-${month}-${day}T${hours}:${minutes}:${seconds}.${milliseconds}${timezone}`;
-    }
-
-    if (this.timeUnit === TimeUnit.Microsecond) {
-      return `${year}-${month}-${day}T${hours}:${minutes}:${seconds}.${milliseconds}000${timezone}`;
-    }
-
-    return `${year}-${month}-${day}T${hours}:${minutes}:${seconds}.${milliseconds}000000${timezone}`;
-  }
-}
diff --git a/glean/src/core/metrics/types/event.ts b/glean/src/core/metrics/types/event.ts
index f968b8dfc..51e3e185e 100644
--- a/glean/src/core/metrics/types/event.ts
+++ b/glean/src/core/metrics/types/event.ts
@@ -6,7 +6,7 @@ import type { CommonMetricData } from "../index.js";
 import { MetricType } from "../index.js";
 import type { ExtraMap} from "../events_database.js";
 import { RecordedEvent } from "../events_database.js";
-import { isUndefined } from "../../utils.js";
+import { getMonotonicNow } from "../../utils.js";
 import { Context } from "../../context.js";
 
 const MAX_LENGTH_EXTRA_KEY_VALUE = 100;
@@ -22,21 +22,6 @@ class EventMetricType extends MetricType {
     this.allowedExtraKeys = allowedExtraKeys;
   }
 
-  /**
-   * An helper function to aid mocking the time in tests.
-   *
-   * This is only meant to be overridden in tests.
-   *
-   * @returns the number of milliseconds since the time origin.
-   */
-  protected getMonotonicNow(): number {
-    // Sadly, `performance.now` is not available outside of browsers, which
-    // means we should get creative to find a proper clock. Fall back to `Date.now`
-    // for now, until bug 1690528 is fixed.
-    const now = isUndefined(performance) ? Date.now() : performance.now();
-    return Math.round(now / 1000);
-  }
-
   /**
    * Record an event by using the information
    * provided by the instance of this class.
@@ -52,7 +37,7 @@ class EventMetricType extends MetricType {
         return;
       }
 
-      const timestamp = this.getMonotonicNow();
+      const timestamp = getMonotonicNow();
 
       // Truncate the extra keys, if needed.
       let truncatedExtra: ExtraMap | undefined = undefined;
diff --git a/glean/src/core/metrics/types/labeled.ts b/glean/src/core/metrics/types/labeled.ts
index e6110df98..c6abfa58c 100644
--- a/glean/src/core/metrics/types/labeled.ts
+++ b/glean/src/core/metrics/types/labeled.ts
@@ -2,11 +2,131 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-import type { CommonMetricData } from "../index.js";
+import type { CommonMetricData, MetricType } from "../index.js";
 import type CounterMetricType from "./counter.js";
 import type BooleanMetricType from "./boolean.js";
 import type StringMetricType from "./string.js";
-import { combineIdentifierAndLabel, OTHER_LABEL } from "./labeled_utils.js";
+import type MetricsDatabase from "../database";
+import type { JSONValue } from "../../utils.js";
+import { Metric } from "../metric.js";
+
+/**
+ * This is an internal metric representation for labeled metrics.
+ *
+ * This can be used to instruct the validators to simply report
+ * whatever is stored internally, without performing any specific
+ * validation.
+ */
+export class LabeledMetric extends Metric<JSONValue, JSONValue> {
+  constructor(v: unknown) {
+    super(v);
+  }
+
+  validate(v: unknown): v is JSONValue {
+    return true;
+  }
+
+  payload(): JSONValue {
+    return this._inner;
+  }
+}
+
+const MAX_LABELS = 16;
+const MAX_LABEL_LENGTH = 61;
+export const OTHER_LABEL = "__other__";
+
+// ** IMPORTANT **
+// When changing this documentation or the regex, be sure to change the same code
+// in the Glean SDK repository as well.
+//
+// This regex is used for matching against labels and should allow for dots,
+// underscores, and/or hyphens. Labels are also limited to starting with either
+// a letter or an underscore character.
+//
+// Some examples of good and bad labels:
+//
+// Good:
+// * `this.is.fine`
+// * `this_is_fine_too`
+// * `this.is_still_fine`
+// * `thisisfine`
+// * `_.is_fine`
+// * `this.is-fine`
+// * `this-is-fine`
+// Bad:
+// * `this.is.not_fine_due_tu_the_length_being_too_long_i_thing.i.guess`
+// * `1.not_fine`
+// * `this.$isnotfine`
+// * `-.not_fine`
+const LABEL_REGEX = /^[a-z_][a-z0-9_-]{0,29}(\.[a-z_][a-z0-9_-]{0,29})*$/;
+
+/**
+ * Combines a metric's base identifier and label.
+ *
+ * @param metricName the metric base identifier
+ * @param label the label
+ *
+ * @returns a string representing the complete metric id including the label.
+ */
+export function combineIdentifierAndLabel(
+  metricName: string,
+  label: string
+): string {
+  return `${metricName}/${label}`;
+}
+
+/**
+ * Checks if the dynamic label stored in the metric data is
+ * valid. If not, record an error and store data in the "__other__"
+ * label.
+ *
+ * @param metricsDatabase the metrics database.
+ * @param metric the metric metadata.
+ *
+ * @returns a valid label that can be used to store data.
+ */
+export async function getValidDynamicLabel(metricsDatabase: MetricsDatabase, metric: MetricType): Promise<string> {
+  // Note that we assume `metric.dynamicLabel` to always be available within this function.
+  // This is a safe assumptions because we should only call `getValidDynamicLabel` if we have
+  // a dynamic label.
+  if (metric.dynamicLabel === undefined) {
+    throw new Error("This point should never be reached.");
+  }
+
+  const key = combineIdentifierAndLabel(metric.baseIdentifier(), metric.dynamicLabel);
+
+  for (const ping of metric.sendInPings) {
+    if (await metricsDatabase.hasMetric(metric.lifetime, ping, metric.type, key)) {
+      return key;
+    }
+  }
+
+  let numUsedKeys = 0;
+  for (const ping of metric.sendInPings) {
+    numUsedKeys += await metricsDatabase.countByBaseIdentifier(
+      metric.lifetime,
+      ping,
+      metric.type,
+      metric.baseIdentifier());
+  }
+
+  let hitError = false;
+  if (numUsedKeys >= MAX_LABELS) {
+    hitError = true;
+  } else if (metric.dynamicLabel.length > MAX_LABEL_LENGTH) {
+    console.error(`label length ${metric.dynamicLabel.length} exceeds maximum of ${MAX_LABEL_LENGTH}`);
+    hitError = true;
+    // TODO: record error in bug 1682574
+  } else if (!LABEL_REGEX.test(metric.dynamicLabel)) {
+    console.error(`label must be snake_case, got '${metric.dynamicLabel}'`);
+    hitError = true;
+    // TODO: record error in bug 1682574
+  }
+
+  return (hitError)
+    ? combineIdentifierAndLabel(metric.baseIdentifier(), OTHER_LABEL)
+    : key;
+}
 
 type SupportedLabeledTypes = CounterMetricType | BooleanMetricType | StringMetricType;
 
diff --git a/glean/src/core/metrics/types/labeled_utils.ts b/glean/src/core/metrics/types/labeled_utils.ts
deleted file mode 100644
index f84e6ca87..000000000
--- a/glean/src/core/metrics/types/labeled_utils.ts
+++ /dev/null
@@ -1,103 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-import type { MetricType } from "..";
-import type MetricsDatabase from "../database";
-
-const MAX_LABELS = 16;
-const MAX_LABEL_LENGTH = 61;
-export const OTHER_LABEL = "__other__";
-
-// ** IMPORTANT **
-// When changing this documentation or the regex, be sure to change the same code
-// in the Glean SDK repository as well.
-//
-// This regex is used for matching against labels and should allow for dots,
-// underscores, and/or hyphens. Labels are also limited to starting with either
-// a letter or an underscore character.
-//
-// Some examples of good and bad labels:
-//
-// Good:
-// * `this.is.fine`
-// * `this_is_fine_too`
-// * `this.is_still_fine`
-// * `thisisfine`
-// * `_.is_fine`
-// * `this.is-fine`
-// * `this-is-fine`
-// Bad:
-// * `this.is.not_fine_due_tu_the_length_being_too_long_i_thing.i.guess`
-// * `1.not_fine`
-// * `this.$isnotfine`
-// * `-.not_fine`
-const LABEL_REGEX = /^[a-z_][a-z0-9_-]{0,29}(\.[a-z_][a-z0-9_-]{0,29})*$/;
-
-/**
- * Combines a metric's base identifier and label.
- *
- * @param metricName the metric base identifier
- * @param label the label
- *
- * @returns a string representing the complete metric id including the label.
- */
-export function combineIdentifierAndLabel(
-  metricName: string,
-  label: string
-): string {
-  return `${metricName}/${label}`;
-}
-
-/**
- * Checks if the dynamic label stored in the metric data is
- * valid. If not, record an error and store data in the "__other__"
- * label.
- *
- * @param metricsDatabase the metrics database.
- * @param metric the metric metadata.
- *
- * @returns a valid label that can be used to store data.
- */
-export async function getValidDynamicLabel(metricsDatabase: MetricsDatabase, metric: MetricType): Promise<string> {
-  // Note that we assume `metric.dynamicLabel` to always be available within this function.
-  // This is a safe assumptions because we should only call `getValidDynamicLabel` if we have
-  // a dynamic label.
-  if (metric.dynamicLabel === undefined) {
-    throw new Error("This point should never be reached.");
-  }
-
-  const key = combineIdentifierAndLabel(metric.baseIdentifier(), metric.dynamicLabel);
-
-  for (const ping of metric.sendInPings) {
-    if (await metricsDatabase.hasMetric(metric.lifetime, ping, metric.type, key)) {
-      return key;
-    }
-  }
-
-  let numUsedKeys = 0;
-  for (const ping of metric.sendInPings) {
-    numUsedKeys += await metricsDatabase.countByBaseIdentifier(
-      metric.lifetime,
-      ping,
-      metric.type,
-      metric.baseIdentifier());
-  }
-
-  let hitError = false;
-  if (numUsedKeys >= MAX_LABELS) {
-    hitError = true;
-  } else if (metric.dynamicLabel.length > MAX_LABEL_LENGTH) {
-    console.error(`label length ${metric.dynamicLabel.length} exceeds maximum of ${MAX_LABEL_LENGTH}`);
-    hitError = true;
-    // TODO: record error in bug 1682574
-  } else if (!LABEL_REGEX.test(metric.dynamicLabel)) {
-    console.error(`label must be snake_case, got '${metric.dynamicLabel}'`);
-    hitError = true;
-    // TODO: record error in bug 1682574
-  }
-
-  return (hitError)
-    ? combineIdentifierAndLabel(metric.baseIdentifier(), OTHER_LABEL)
-    : key;
-}
diff --git a/glean/src/core/metrics/types/string.ts b/glean/src/core/metrics/types/string.ts
index 764e6530a..9210c3e07 100644
--- a/glean/src/core/metrics/types/string.ts
+++ b/glean/src/core/metrics/types/string.ts
@@ -4,8 +4,33 @@
 
 import type { CommonMetricData } from "../index.js";
 import { MetricType } from "../index.js";
-import { MAX_LENGTH_VALUE, StringMetric } from "./string_metric.js";
 import { Context } from "../../context.js";
+import { Metric } from "../metric.js";
+import { isString } from "../../utils.js";
+
+export const MAX_LENGTH_VALUE = 100;
+
+export class StringMetric extends Metric<string, string> {
+  constructor(v: unknown) {
+    super(v);
+  }
+
+  validate(v: unknown): v is string {
+    if (!isString(v)) {
+      return false;
+    }
+
+    if (v.length > MAX_LENGTH_VALUE) {
+      return false;
+    }
+
+    return true;
+  }
+
+  payload(): string {
+    return this._inner;
+  }
+}
 
 /**
  * A string metric.
diff --git a/glean/src/core/metrics/types/string_metric.ts b/glean/src/core/metrics/types/string_metric.ts
deleted file mode 100644
index 2e42c1a2f..000000000
--- a/glean/src/core/metrics/types/string_metric.ts
+++ /dev/null
@@ -1,30 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-import { Metric } from "../metric.js";
-import { isString } from "../../utils.js";
-
-export const MAX_LENGTH_VALUE = 100;
-
-export class StringMetric extends Metric<string, string> {
-  constructor(v: unknown) {
-    super(v);
-  }
-
-  validate(v: unknown): v is string {
-    if (!isString(v)) {
-      return false;
-    }
-
-    if (v.length > MAX_LENGTH_VALUE) {
-      return false;
-    }
-
-    return true;
-  }
-
-  payload(): string {
-    return this._inner;
-  }
-}
diff --git a/glean/src/core/metrics/types/timespan.ts b/glean/src/core/metrics/types/timespan.ts
new file mode 100644
index 000000000..60728b5b9
--- /dev/null
+++ b/glean/src/core/metrics/types/timespan.ts
@@ -0,0 +1,203 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import type { CommonMetricData} from "../index.js";
+import type { JSONValue } from "../../utils.js";
+import TimeUnit from "../time_unit.js";
+import { MetricType } from "../index.js";
+import { isString, isObject, isNumber, isUndefined, getMonotonicNow } from "../../utils.js";
+import { Metric } from "../metric.js";
+import { Context } from "../../context.js";
+
+export type TimespanInternalRepresentation = {
+  // The time unit of the metric type at the time of recording.
+  timeUnit: TimeUnit,
+  // The timespan in milliseconds.
+  timespan: number,
+};
+export class TimespanMetric extends Metric<TimespanInternalRepresentation, number> {
+  constructor(v: unknown) {
+    super(v);
+  }
+
+  validate(v: unknown): v is TimespanInternalRepresentation {
+    if (!isObject(v) || Object.keys(v).length !== 2) {
+      return false;
+    }
+
+    const timeUnitVerification = "timeUnit" in v && isString(v.timeUnit) && Object.values(TimeUnit).includes(v.timeUnit as TimeUnit);
+    const timespanVerification = "timespan" in v && isNumber(v.timespan) && v.timespan >= 0;
+    if (!timeUnitVerification || !timespanVerification) {
+      return false;
+    }
+
+    return true;
+  }
+
+  payload(): number {
+    switch(this._inner.timeUnit) {
+    case TimeUnit.Nanosecond:
+      return this._inner.timespan * 10**6;
+    case TimeUnit.Microsecond:
+      return this._inner.timespan * 10**3;
+    case TimeUnit.Millisecond:
+      return this._inner.timespan;
+    case TimeUnit.Second:
+      return Math.round(this._inner.timespan / 1000);
+    case TimeUnit.Minute:
+      return Math.round(this._inner.timespan / 1000 / 60);
+    case TimeUnit.Hour:
+      return Math.round(this._inner.timespan / 1000 / 60 / 60);
+    case TimeUnit.Day:
+      return Math.round(this._inner.timespan / 1000 / 60 / 60 / 24);
+    }
+  }
+}
+
+/**
+ * A timespan metric.
+ *
+ * Timespans are used to make a measurement of how much time is spent in a particular task.
+ */
+class TimespanMetricType extends MetricType {
+  private timeUnit: TimeUnit;
+  startTime?: number;
+
+  constructor(meta: CommonMetricData, timeUnit: string) {
+    super("timespan", meta);
+    this.timeUnit = timeUnit as TimeUnit;
+  }
+
+  /**
+   * Starts tracking time for the provided metric.
+   *
+   * This records an error if it's already tracking time (i.e. start was
+   * already called with no corresponding `stop()`. In which case the original
+   * start time will be preserved.
+   */
+  start(): void {
+    // Get the start time outside of the dispatched task so that
+    // it is the time this function is called and not the time the task is executed.
+    const startTime = getMonotonicNow();
+
+    Context.dispatcher.launch(async () => {
+      if (!this.shouldRecord(Context.uploadEnabled)) {
+        return;
+      }
+
+      if (!isUndefined(this.startTime)) {
+        // TODO: record error once Bug 1682574 is resolved.
+        console.error("Timespan already started.");
+        return;
+      }
+
+      this.startTime = startTime;
+
+      return Promise.resolve();
+    });
+  }
+
+  /**
+   * Stops tracking time for the provided metric. Sets the metric to the elapsed time.
+   *
+   * This will record an error if no `start()` was called.
+   */
+  stop(): void {
+    // Get the stop time outside of the dispatched task so that
+    // it is the time this function is called and not the time the task is executed.
+    const stopTime = getMonotonicNow();
+
+    Context.dispatcher.launch(async () => {
+      if (!this.shouldRecord(Context.uploadEnabled)) {
+        // Reset timer when disabled, so that we don't record timespans across
+        // disabled/enabled toggling.
+        this.startTime = undefined;
+        return;
+      }
+
+      if (isUndefined(this.startTime)) {
+        // TODO: record error once Bug 1682574 is resolved.
+        console.error("Timespan not running.");
+        return;
+      }
+
+      const elapsed = stopTime - this.startTime;
+      this.startTime = undefined;
+
+      if (elapsed < 0) {
+        // TODO: record error once Bug 1682574 is resolved.
+        console.error("Timespan was negative.");
+        return;
+      }
+
+      let reportValueExists = false;
+      const transformFn = ((elapsed) => {
+        return (old?: JSONValue): TimespanMetric => {
+          let metric: TimespanMetric;
+          try {
+            metric = new TimespanMetric(old);
+            // If creating the metric didn't error,
+            // there is a valid timespan already recorded for this metric.
+            reportValueExists = true;
+          } catch {
+            metric = new TimespanMetric({
+              timespan: elapsed,
+              timeUnit: this.timeUnit,
+            });
+          }
+
+          return metric;
+        };
+      })(elapsed);
+
+      await Context.metricsDatabase.transform(this, transformFn);
+
+      if (reportValueExists) {
+        // TODO: record error once Bug 1682574 is resolved.
+        console.error("Timespan value already recorded. New value discarded.");
+      }
+    });
+  }
+
+  /**
+   * Aborts a previous `start()` call.
+   *
+   * No error is recorded if no `start()` was called.
+   */
+  cancel(): void {
+    Context.dispatcher.launch(() => {
+      this.startTime = undefined;
+      return Promise.resolve();
+    });
+  }
+
+  /**
+   * **Test-only API.**
+   *
+   * Gets the currently stored value as a number.
+   *
+   * This doesn't clear the stored value.
+   *
+   * TODO: Only allow this function to be called on test mode (depends on Bug 1682771).
+   *
+   * @param ping the ping from which we want to retrieve this metrics value from.
+   *        Defaults to the first value in `sendInPings`.
+   *
+   * @returns The value found in storage or `undefined` if nothing was found.
+   */
+  async testGetValue(ping: string = this.sendInPings[0]): Promise<number | undefined> {
+    let value: TimespanInternalRepresentation | undefined;
+    await Context.dispatcher.testLaunch(async () => {
+      value = await Context.metricsDatabase.getMetric<TimespanInternalRepresentation>(ping, this);
+    });
+
+    if (value) {
+      // `payload` will truncate to the defined time_unit at the time of recording.
+      return (new TimespanMetric(value)).payload();
+    }
+  }
+}
+
+export default TimespanMetricType;
+
diff --git a/glean/src/core/metrics/types/uuid.ts b/glean/src/core/metrics/types/uuid.ts
index 551bf473f..4647bd0b9 100644
--- a/glean/src/core/metrics/types/uuid.ts
+++ b/glean/src/core/metrics/types/uuid.ts
@@ -4,9 +4,33 @@
 
 import type { CommonMetricData } from "../index.js";
 import { MetricType } from "../index.js";
-import { generateUUIDv4 } from "../../utils.js";
-import { UUIDMetric } from "./uuid_metric.js";
+import { generateUUIDv4, isString } from "../../utils.js";
 import { Context } from "../../context.js";
+import { validate as UUIDvalidate } from "uuid";
+import { KNOWN_CLIENT_ID } from "../../constants.js";
+import { Metric } from "../metric.js";
+
+export class UUIDMetric extends Metric<string, string> {
+  constructor(v: unknown) {
+    super(v);
+  }
+
+  validate(v: unknown): v is string {
+    if (!isString(v)) {
+      return false;
+    }
+
+    if (v === KNOWN_CLIENT_ID) {
+      return true;
+    }
+
+    return UUIDvalidate(v);
+  }
+
+  payload(): string {
+    return this._inner;
+  }
+}
 
 /**
  *  An UUID metric.
diff --git a/glean/src/core/metrics/types/uuid_metric.ts b/glean/src/core/metrics/types/uuid_metric.ts
deleted file mode 100644
index 3ed116545..000000000
--- a/glean/src/core/metrics/types/uuid_metric.ts
+++ /dev/null
@@ -1,30 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-import { validate as UUIDvalidate } from "uuid";
-import { KNOWN_CLIENT_ID } from "../../constants.js";
-import { Metric } from "../metric.js";
-import { isString } from "../../utils.js";
-
-export class UUIDMetric extends Metric<string, string> {
-  constructor(v: unknown) {
-    super(v);
-  }
-
-  validate(v: unknown): v is string {
-    if (!isString(v)) {
-      return false;
-    }
-
-    if (v === KNOWN_CLIENT_ID) {
-      return true;
-    }
-
-    return UUIDvalidate(v);
-  }
-
-  payload(): string {
-    return this._inner;
-  }
-}
diff --git a/glean/src/core/metrics/utils.ts b/glean/src/core/metrics/utils.ts
index d66af5008..94e013fd6 100644
--- a/glean/src/core/metrics/utils.ts
+++ b/glean/src/core/metrics/utils.ts
@@ -2,15 +2,17 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-import { LabeledMetric } from "./index.js";
+
 import type { Metric } from "./metric.js";
 import type { JSONValue } from "../utils.js";
 
-import { BooleanMetric } from "./types/boolean_metric.js";
-import { CounterMetric } from "./types/counter_metric.js";
-import { DatetimeMetric } from "./types/datetime_metric.js";
-import { StringMetric } from "./types/string_metric.js";
-import { UUIDMetric } from "./types/uuid_metric.js";
+import { LabeledMetric } from "./types/labeled.js";
+import { BooleanMetric } from "./types/boolean.js";
+import { CounterMetric } from "./types/counter.js";
+import { DatetimeMetric } from "./types/datetime.js";
+import { StringMetric } from "./types/string.js";
+import { TimespanMetric } from "./types/timespan.js";
+import { UUIDMetric } from "./types/uuid.js";
 
 /**
  * A map containing all supported internal metrics and its constructors.
@@ -25,6 +27,7 @@ const METRIC_MAP: {
   "labeled_counter": LabeledMetric,
   "labeled_string": LabeledMetric,
   "string": StringMetric,
+  "timespan": TimespanMetric,
   "uuid": UUIDMetric,
 });
 
diff --git a/glean/src/core/pings/maker.ts b/glean/src/core/pings/maker.ts
index d3a206a03..a726fcc12 100644
--- a/glean/src/core/pings/maker.ts
+++ b/glean/src/core/pings/maker.ts
@@ -3,17 +3,17 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 import { GLEAN_SCHEMA_VERSION, GLEAN_VERSION, PING_INFO_STORAGE, CLIENT_INFO_STORAGE } from "../constants.js";
-import CounterMetricType from "../metrics/types/counter.js";
-import { CounterMetric } from "../metrics/types/counter_metric.js";
-import DatetimeMetricType from "../metrics/types/datetime.js";
-import { DatetimeMetric } from "../metrics/types/datetime_metric.js";
-import TimeUnit from "../metrics/time_unit.js";
 import type { ClientInfo, PingInfo, PingPayload } from "../pings/ping_payload.js";
 import type CommonPingData from "./common_ping_data.js";
-import CoreEvents from "../events/index.js";
 import type MetricsDatabase from "../metrics/database.js";
 import type EventsDatabase from "../metrics/events_database.js";
 import type { DebugOptions } from "../debug_options.js";
+import CounterMetricType from "../metrics/types/counter.js";
+import { CounterMetric } from "../metrics/types/counter.js";
+import DatetimeMetricType from "../metrics/types/datetime.js";
+import { DatetimeMetric } from "../metrics/types/datetime.js";
+import TimeUnit from "../metrics/time_unit.js";
+import CoreEvents from "../events/index.js";
 import { Lifetime } from "../metrics/lifetime.js";
 import { Context } from "../context.js";
 
diff --git a/glean/src/core/pings/ping_payload.ts b/glean/src/core/pings/ping_payload.ts
index 6fb335025..54a8f3637 100644
--- a/glean/src/core/pings/ping_payload.ts
+++ b/glean/src/core/pings/ping_payload.ts
@@ -2,7 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-import type { Metrics } from "../metrics/metrics_interface.js";
+import type { Metrics } from "../metrics/index.js";
 import type { JSONObject, JSONArray } from "../utils.js";
 
 export interface PingInfo extends JSONObject {
diff --git a/glean/src/core/utils.ts b/glean/src/core/utils.ts
index 3faaa1f4e..68d83536e 100644
--- a/glean/src/core/utils.ts
+++ b/glean/src/core/utils.ts
@@ -159,3 +159,17 @@ export function generateUUIDv4(): string {
     });
   }
 }
+
+/**
+ * A helper function to aid mocking the time in tests.
+ *
+ * This is only meant to be overridden in tests.
+ *
+ * @returns The number of milliseconds since the time origin.
+ */
+export function getMonotonicNow(): number {
+  // Sadly, `performance.now` is not available on Qt, which
+  // means we should get creative to find a proper clock for that platform.
+  // Fall back to `Date.now` for now, until bug 1690528 is fixed.
+  return typeof performance === "undefined" ? Date.now() : performance.now();
+}
diff --git a/glean/tests/core/metrics/database.spec.ts b/glean/tests/core/metrics/database.spec.ts
index 877429cb8..3421d0215 100644
--- a/glean/tests/core/metrics/database.spec.ts
+++ b/glean/tests/core/metrics/database.spec.ts
@@ -6,7 +6,7 @@ import assert from "assert";
 
 import Database, { isValidInternalMetricsRepresentation } from "../../../src/core/metrics/database";
 import StringMetricType from "../../../src/core/metrics/types/string";
-import { StringMetric } from "../../../src/core/metrics/types/string_metric";
+import { StringMetric } from "../../../src/core/metrics/types/string";
 import type { JSONValue } from "../../../src/core/utils";
 import Glean from "../../../src/core/glean";
 import { Lifetime } from "../../../src/core/metrics/lifetime";
diff --git a/glean/tests/core/metrics/datetime.spec.ts b/glean/tests/core/metrics/datetime.spec.ts
index a635307e8..f66e1e2e6 100644
--- a/glean/tests/core/metrics/datetime.spec.ts
+++ b/glean/tests/core/metrics/datetime.spec.ts
@@ -7,7 +7,7 @@ import sinon from "sinon";
 
 import Glean from "../../../src/core/glean";
 import DatetimeMetricType from "../../../src/core/metrics/types/datetime";
-import { DatetimeMetric } from "../../../src/core/metrics/types/datetime_metric";
+import { DatetimeMetric } from "../../../src/core/metrics/types/datetime";
 import TimeUnit from "../../../src/core/metrics/time_unit";
 import { Lifetime } from "../../../src/core/metrics/lifetime";
 import { Context } from "../../../src/core/context";
diff --git a/glean/tests/core/metrics/event.spec.ts b/glean/tests/core/metrics/event.spec.ts
index 69750f62b..5be83a8aa 100644
--- a/glean/tests/core/metrics/event.spec.ts
+++ b/glean/tests/core/metrics/event.spec.ts
@@ -2,21 +2,12 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-import { performance } from "perf_hooks";
 import assert from "assert";
 
 import Glean from "../../../src/core/glean";
 import EventMetricType from "../../../src/core/metrics/types/event";
 import { Lifetime } from "../../../src/core/metrics/lifetime";
 
-// A test event type that exclusively overrides the
-// monotonic timer.
-class TestEventMetricType extends EventMetricType {
-  getMonotonicNow(): number {
-    return Math.round(performance.now() / 1000);
-  }
-}
-
 describe("EventMetric", function() {
   const testAppId = `gleanjs.test.${this.title}`;
 
@@ -25,7 +16,7 @@ describe("EventMetric", function() {
   });
 
   it("the API records to its storage engine", async function () {
-    const click = new TestEventMetricType({
+    const click = new EventMetricType({
       category: "ui",
       name: "click",
       sendInPings: ["store1"],
@@ -58,7 +49,7 @@ describe("EventMetric", function() {
   });
 
   it("the API records when category is empty", async function () {
-    const click = new TestEventMetricType({
+    const click = new EventMetricType({
       category: "",
       name: "click",
       sendInPings: ["store1"],
@@ -86,7 +77,7 @@ describe("EventMetric", function() {
   });
 
   it("disabled events must not record data", async function () {
-    const click = new TestEventMetricType({
+    const click = new EventMetricType({
       category: "ui",
       name: "click",
       sendInPings: ["store1"],
@@ -101,7 +92,7 @@ describe("EventMetric", function() {
   });
 
   it("events should not record when upload is disabled", async function () {
-    const click = new TestEventMetricType({
+    const click = new EventMetricType({
       category: "ui",
       name: "click",
       sendInPings: ["store1"],
@@ -133,7 +124,7 @@ describe("EventMetric", function() {
   it("records properly without optional arguments", async function () {
     const pings = ["store1", "store2"];
 
-    const metric = new TestEventMetricType({
+    const metric = new EventMetricType({
       category: "telemetry",
       name: "test_event_no_optional",
       sendInPings: pings,
@@ -156,7 +147,7 @@ describe("EventMetric", function() {
   it("records properly with optional arguments", async function () {
     const pings = ["store1", "store2"];
 
-    const metric = new TestEventMetricType({
+    const metric = new EventMetricType({
       category: "telemetry",
       name: "test_event_with_optional",
       sendInPings: pings,
@@ -186,7 +177,7 @@ describe("EventMetric", function() {
   it.skip("bug 1690253: send an event ping when it fills up");
 
   it("extra keys must be recorded and truncated if needed", async function () {
-    const testEvent = new TestEventMetricType({
+    const testEvent = new EventMetricType({
       category: "ui",
       name: "testEvent",
       sendInPings: ["store1"],
diff --git a/glean/tests/core/metrics/labeled.spec.ts b/glean/tests/core/metrics/labeled.spec.ts
index cd58fced3..64d2b09d7 100644
--- a/glean/tests/core/metrics/labeled.spec.ts
+++ b/glean/tests/core/metrics/labeled.spec.ts
@@ -4,8 +4,8 @@
 
 import assert from "assert";
 import sinon from "sinon";
-import { Context } from "../../../src/core/context";
 
+import { Context } from "../../../src/core/context";
 import Glean from "../../../src/core/glean";
 import { Lifetime } from "../../../src/core/metrics/lifetime";
 import BooleanMetricType from "../../../src/core/metrics/types/boolean";
diff --git a/glean/tests/core/metrics/string.spec.ts b/glean/tests/core/metrics/string.spec.ts
index a509d3870..7f343f8a7 100644
--- a/glean/tests/core/metrics/string.spec.ts
+++ b/glean/tests/core/metrics/string.spec.ts
@@ -7,7 +7,7 @@ import assert from "assert";
 import Glean from "../../../src/core/glean";
 import StringMetricType from "../../../src/core/metrics/types/string";
 import { Lifetime } from "../../../src/core/metrics/lifetime";
-import { MAX_LENGTH_VALUE } from "../../../src/core/metrics/types/string_metric";
+import { MAX_LENGTH_VALUE } from "../../../src/core/metrics/types/string";
 import { Context } from "../../../src/core/context";
 
 describe("StringMetric", function() {
diff --git a/glean/tests/core/metrics/timespan.spec.ts b/glean/tests/core/metrics/timespan.spec.ts
new file mode 100644
index 000000000..838bc8e19
--- /dev/null
+++ b/glean/tests/core/metrics/timespan.spec.ts
@@ -0,0 +1,302 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import assert from "assert";
+import sinon from "sinon";
+
+import { Context } from "../../../src/core/context";
+import Glean from "../../../src/core/glean";
+import { Lifetime } from "../../../src/core/metrics/lifetime";
+import TimeUnit from "../../../src/core/metrics/time_unit";
+import TimespanMetricType, { TimespanMetric } from "../../../src/core/metrics/types/timespan";
+
+const sandbox = sinon.createSandbox();
+
+describe("TimespanMetric", function() {
+  const testAppId = `gleanjs.test.${this.title}`;
+
+  beforeEach(async function() {
+    await Glean.testResetGlean(testAppId);
+  });
+
+  afterEach(function () {
+    sandbox.restore();
+  });
+
+  it("timespan internal representation validation works as expected", function () {
+    // Invalid objects
+    assert.throws(() => new TimespanMetric(undefined));
+    assert.throws(() => new TimespanMetric(null));
+    assert.throws(() => new TimespanMetric({}));
+    assert.throws(() => new TimespanMetric({ rubbish: "garbage" }));
+    assert.throws(() => new TimespanMetric({ rubbish: "garbage", timeUnit: "milliseconds" }));
+
+    // Invalid time units
+    assert.throws(() => new TimespanMetric({ timeUnit: "garbage", timespan: 10 }));
+    assert.throws(() => new TimespanMetric({ timeUnit: null, timespan: 10 }));
+    assert.throws(() => new TimespanMetric({ timeUnit: "hour" }));
+
+    // Invalid timespans
+    assert.throws(() => new TimespanMetric({ timeUnit: "hour", timespan: -300 }));
+    assert.throws(() => new TimespanMetric({ timeUnit: "hour", timespan: "aaaaaaaaaaaaaaaaaaaaaaaa" }));
+    assert.throws(() => new TimespanMetric({ timespan: 10 }));
+
+    // Valid values
+    assert.doesNotThrow(() => new TimespanMetric({ timeUnit: "millisecond", timespan: 300 }));
+  });
+
+  it("attempting to get the value of a metric that hasn't been recorded doesn't error", async function() {
+    const metric = new TimespanMetricType({
+      category: "aCategory",
+      name: "aTimespan",
+      sendInPings: ["aPing", "twoPing", "threePing"],
+      lifetime: Lifetime.Ping,
+      disabled: false
+    }, "millisecond");
+
+    assert.strictEqual(await metric.testGetValue("aPing"), undefined);
+  });
+
+  it("attempting to start/stop when glean upload is disabled is a no-op", async function() {
+    Glean.setUploadEnabled(false);
+
+    const metric = new TimespanMetricType({
+      category: "aCategory",
+      name: "aTimespan",
+      sendInPings: ["aPing", "twoPing", "threePing"],
+      lifetime: Lifetime.Ping,
+      disabled: false
+    }, "millisecond");
+
+    metric.start();
+    metric.stop();
+
+    assert.strictEqual(await metric.testGetValue("aPing"), undefined);
+  });
+
+  it("ping payload is correct", async function() {
+    const fakeDateNow = sandbox.stub(Date, "now");
+    fakeDateNow.onCall(0).callsFake(() => 0);
+    fakeDateNow.onCall(1).callsFake(() => 100);
+
+    const metric = new TimespanMetricType({
+      category: "aCategory",
+      name: "aTimespan",
+      sendInPings: ["aPing"],
+      lifetime: Lifetime.Ping,
+      disabled: false
+    }, "millisecond");
+
+    metric.start();
+    metric.stop();
+    assert.strictEqual(await metric.testGetValue("aPing"), 100);
+
+    const snapshot = await Context.metricsDatabase.getPingMetrics("aPing", true);
+    assert.deepStrictEqual(snapshot, {
+      "timespan": {
+        "aCategory.aTimespan": 100
+      }
+    });
+  });
+
+  it("recording APIs properly sets the value in all pings", async function() {
+    const fakeDateNow = sandbox.stub(Date, "now");
+    fakeDateNow.onCall(0).callsFake(() => 0);
+    fakeDateNow.onCall(1).callsFake(() => 100);
+
+    const metric = new TimespanMetricType({
+      category: "aCategory",
+      name: "aTimespan",
+      sendInPings: ["aPing", "twoPing", "threePing"],
+      lifetime: Lifetime.Ping,
+      disabled: false
+    }, "millisecond");
+
+    metric.start();
+    metric.stop();
+    assert.strictEqual(await metric.testGetValue("aPing"), 100);
+    assert.strictEqual(await metric.testGetValue("twoPing"), 100);
+    assert.strictEqual(await metric.testGetValue("threePing"), 100);
+  });
+
+  it("truncation works", async function() {
+    const testCases = [
+      {
+        unit: TimeUnit.Nanosecond,
+        expected: 3600000000000,
+      },
+      {
+        unit: TimeUnit.Microsecond,
+        expected: 3600000000,
+      },
+      {
+        unit: TimeUnit.Millisecond,
+        expected: 3600000,
+      },
+      {
+        unit: TimeUnit.Second,
+        expected: 3600,
+      },
+      {
+        unit: TimeUnit.Minute,
+        expected: 60,
+      },
+      {
+        unit: TimeUnit.Hour,
+        expected: 1,
+      },
+      {
+        unit: TimeUnit.Day,
+        expected: 0,
+      },
+    ];
+
+    for (const testCase of testCases) {
+      const fakeDateNow = sandbox.stub(Date, "now");
+      fakeDateNow.onCall(0).callsFake(() => 0);
+      fakeDateNow.onCall(1).callsFake(() => 3600000); // One hour.
+
+      const metric = new TimespanMetricType({
+        category: "aCategory",
+        name: `aDatetimeMetric_${testCase.unit}`,
+        sendInPings: ["aPing"],
+        lifetime: Lifetime.Ping,
+        disabled: false
+      }, testCase.unit);
+
+      metric.start();
+      metric.stop();
+      assert.strictEqual(await metric.testGetValue("aPing"), testCase.expected);
+
+      sandbox.restore();
+    }
+  });
+
+  it("second timer run is skipped", async function() {
+    const fakeDateNow = sandbox.stub(Date, "now");
+    // First check, duration: 100
+    fakeDateNow.onCall(0).callsFake(() => 0);
+    fakeDateNow.onCall(1).callsFake(() => 100);
+    // Second check, duration 99
+    fakeDateNow.onCall(2).callsFake(() => 101);
+    fakeDateNow.onCall(3).callsFake(() => 200);
+
+    // TODO: check number of recorded errors instead once Bug 1682574 is resolved.
+    const consoleErrorSpy = sandbox.spy(console, "error");
+
+    const metric = new TimespanMetricType({
+      category: "aCategory",
+      name: "aTimespan",
+      sendInPings: ["aPing"],
+      lifetime: Lifetime.Ping,
+      disabled: false
+    }, "millisecond");
+
+    metric.start();
+    metric.stop();
+    assert.strictEqual(await metric.testGetValue("aPing"), 100);
+
+    // No error should be logged here: we had no prior value stored.
+    assert.deepStrictEqual(consoleErrorSpy.callCount, 0);
+
+    metric.start();
+    metric.stop();
+    // First value should not be overwritten
+    assert.strictEqual(await metric.testGetValue("aPing"), 100);
+
+    // Make sure that the error has been logged: we had a stored value,
+    // the new measurement was dropped.
+    assert.deepStrictEqual(consoleErrorSpy.callCount, 1);
+  });
+
+  it("cancel does not store and clears start time", async function() {
+    const metric = new TimespanMetricType({
+      category: "aCategory",
+      name: "aTimespan",
+      sendInPings: ["aPing"],
+      lifetime: Lifetime.Ping,
+      disabled: false
+    }, "millisecond");
+
+    metric.start();
+    metric.cancel();
+    assert.strictEqual(await metric.testGetValue("aPing"), undefined);
+    assert.strictEqual(metric["startTime"], undefined);
+  });
+
+  it("nothing is stored before stop", async function() {
+    const fakeDateNow = sandbox.stub(Date, "now");
+    fakeDateNow.onCall(0).callsFake(() => 0);
+    fakeDateNow.onCall(1).callsFake(() => 100);
+
+    const metric = new TimespanMetricType({
+      category: "aCategory",
+      name: "aTimespan",
+      sendInPings: ["aPing"],
+      lifetime: Lifetime.Ping,
+      disabled: false
+    }, "millisecond");
+
+    metric.start();
+    assert.strictEqual(await metric.testGetValue("aPing"), undefined);
+
+    metric.stop();
+    assert.strictEqual(await metric.testGetValue("aPing"), 100);
+  });
+
+  it("timespan is not tracked across upload toggle", async function() {
+    const metric = new TimespanMetricType({
+      category: "aCategory",
+      name: "aTimespan",
+      sendInPings: ["aPing"],
+      lifetime: Lifetime.Ping,
+      disabled: false
+    }, "millisecond");
+
+    // Timer is started.
+    metric.start();
+    // User disables telemetry upload.
+    Glean.setUploadEnabled(false);
+    // App code eventually stops the timer.
+    // We should clear internal state as upload is disabled.
+    metric.stop();
+
+    // App code eventually starts the timer again.
+    // Upload is disabled, so this should not have any effect.
+    metric.start();
+    // User enables telemetry upload again.
+    Glean.setUploadEnabled(true);
+    // App code eventually stops the timer.
+    // None should be running.
+    metric.stop();
+
+    // Nothing should have been recorded.
+    assert.strictEqual(await metric.testGetValue("aPing"), undefined);
+
+    // TODO: Make sure also incalid state error was recorded.
+  });
+
+  it("time cannot go backwards", async function() {
+    const fakeDateNow = sandbox.stub(Date, "now");
+    fakeDateNow.onCall(0).callsFake(() => 100);
+    fakeDateNow.onCall(1).callsFake(() => 0);
+
+    const metric = new TimespanMetricType({
+      category: "aCategory",
+      name: "aTimespan",
+      sendInPings: ["aPing"],
+      lifetime: Lifetime.Ping,
+      disabled: false
+    }, "millisecond");
+
+    // TODO: check number of recorded errors instead once Bug 1682574 is resolved.
+    const consoleErrorSpy = sandbox.spy(console, "error");
+
+    metric.start();
+    metric.stop();
+    assert.strictEqual(await metric.testGetValue("aPing"), undefined);
+
+    assert.deepStrictEqual(consoleErrorSpy.callCount, 1);
+  });
+});