fix(datetime): display time in user's timezone after selection (#25694)

Resolves #25693

Author: sean-perkins

core/src/components/datetime/test/format.spec.ts

@@ -5,6 +5,7 @@ import {
   addTimePadding,
   getMonthAndYear,
   getLocalizedDayPeriod,
+  getLocalizedTime,
 } from '../utils/format';
 
 describe('generateDayAriaLabel()', () => {
@@ -99,3 +100,59 @@ describe('getLocalizedDayPeriod', () => {
     expect(getLocalizedDayPeriod('en-US', 'pm'));
   });
 });
+
+describe('getLocalizedTime', () => {
+  describe('with a timezone offset', () => {
+    it('should ignore the offset and localize the time to PM', () => {
+      const datetimeParts = {
+        day: 1,
+        month: 1,
+        year: 2022,
+        hour: 13,
+        minute: 40,
+        tzOffset: -240,
+      };
+
+      expect(getLocalizedTime('en-US', datetimeParts, false)).toEqual('1:40 PM');
+    });
+
+    it('should ignore the offset and localize the time to AM', () => {
+      const datetimeParts = {
+        day: 1,
+        month: 1,
+        year: 2022,
+        hour: 9,
+        minute: 40,
+        tzOffset: -240,
+      };
+
+      expect(getLocalizedTime('en-US', datetimeParts, false)).toEqual('9:40 AM');
+    });
+  });
+
+  it('should localize the time to PM', () => {
+    const datetimeParts = {
+      day: 1,
+      month: 1,
+      year: 2022,
+      hour: 13,
+      minute: 40,
+      tzOffset: 0,
+    };
+
+    expect(getLocalizedTime('en-US', datetimeParts, false)).toEqual('1:40 PM');
+  });
+
+  it('should localize the time to AM', () => {
+    const datetimeParts = {
+      day: 1,
+      month: 1,
+      year: 2022,
+      hour: 9,
+      minute: 40,
+      tzOffset: 0,
+    };
+
+    expect(getLocalizedTime('en-US', datetimeParts, false)).toEqual('9:40 AM');
+  });
+});

core/src/components/datetime/utils/format.ts

@@ -20,7 +20,15 @@ export const getLocalizedTime = (locale: string, refParts: DatetimeParts, use24H
     minute: 'numeric',
     timeZone: 'UTC',
     hour12: !use24Hour,
-  }).format(new Date(convertDataToISO(refParts)));
+  }).format(
+    new Date(
+      convertDataToISO({
+        ...refParts,
+        // TODO: FW-1831 will remove the need to manually set the tzOffset to undefined
+        tzOffset: undefined,
+      })
+    )
+  );
 };
 
 /**