diff --git a/CHANGELOG.md b/CHANGELOG.md
index af40717856..36b66eb98c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -30,6 +30,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 -  Fixes [#5050](https://github.com/microsoft/BotFramework-WebChat/issues/5050). Fixed focus should not blur briefly after tapping on a suggested action, by [@compulim](https://github.com/compulim), in PR [#5097](https://github.com/microsoft/BotFramework-WebChat/issues/pull/5097)
 -  Fixes [#5111](https://github.com/microsoft/BotFramework-WebChat/issues/5111). Fixed keyboard help screen to use HTML description list, by [@compulim](https://github.com/compulim), in PR [#5116](https://github.com/microsoft/BotFramework-WebChat/issues/pull/5116)
+-  Fixes [#5080](https://github.com/microsoft/BotFramework-WebChat/issues/5080). Fixed `dateToLocaleISOString` for handling sub-hour, by [@marclundgren](https://github.com/marclundgren), in PR [#5114](https://github.com/microsoft/BotFramework-WebChat/pull/5114)
 
 ### Changed
 
diff --git a/packages/core/src/utils/dateToLocaleISOString.newfoundland.spec.js b/packages/core/src/utils/dateToLocaleISOString.newfoundland.spec.js
new file mode 100644
index 0000000000..0f783d687a
--- /dev/null
+++ b/packages/core/src/utils/dateToLocaleISOString.newfoundland.spec.js
@@ -0,0 +1,14 @@
+/**
+ * @jest-environment ../../../__tests__/setup/jestNodeEnvironmentWithTimezone.js
+ * @timezone America/St_Johns
+ */
+
+import dateToLocaleISOString from './dateToLocaleISOString';
+
+test('formatting a time in Cananda, Newfoundland timezone', () => {
+  // eslint-disable-next-line no-magic-numbers
+  const date = new Date(Date.UTC(2000, 0, 1, 0, 12, 34, 567));
+  const actual = dateToLocaleISOString(date);
+
+  expect(actual).toMatchInlineSnapshot(`"1999-12-31T20:42:34.567-03:30"`);
+});
diff --git a/packages/core/src/utils/dateToLocaleISOString.ts b/packages/core/src/utils/dateToLocaleISOString.ts
index 25589d7e8e..3d3c7f16f0 100644
--- a/packages/core/src/utils/dateToLocaleISOString.ts
+++ b/packages/core/src/utils/dateToLocaleISOString.ts
@@ -45,9 +45,11 @@ export default function dateToLocaleISOString(date: Date): string {
   // "yyyy-MM-DDTHH:mm:ss.fff+08:00" for GMT+08
   // "yyyy-MM-DDTHH:mm:ss.fffZ" for UTC
 
+  const absoluteTimezoneOffset = ~~Math.abs(timezoneOffset);
+
   return `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}T${pad(date.getHours())}:${pad(
     date.getMinutes()
   )}:${pad(date.getSeconds())}.${pad(date.getMilliseconds(), 3)}${
-    timezoneOffset ? `${timezoneSign}${pad(~~(Math.abs(timezoneOffset) / 60))}:${pad(timezoneOffset % 60)}` : 'Z'
+    timezoneOffset ? `${timezoneSign}${pad(~~(absoluteTimezoneOffset / 60))}:${pad(absoluteTimezoneOffset % 60)}` : 'Z'
   }`;
 }