regression: timezone field blank for legacy aliases

apps/meteor/client/hooks/useTimezoneNameList.ts

@@ -2,7 +2,8 @@ import { useMemo } from 'react';
 
 const getTimeZoneNames = (): string[] => {
 	const intl = Intl as typeof Intl & { supportedValuesOf?(key: 'timeZone'): string[] };
-	return typeof intl.supportedValuesOf === 'function' ? intl.supportedValuesOf('timeZone') : [];
+	const names = typeof intl.supportedValuesOf === 'function' ? intl.supportedValuesOf('timeZone') : [];
+	return names.includes('UTC') ? names : ['UTC', ...names];
 };
 
 export const useTimezoneNameList = (): string[] => useMemo(() => getTimeZoneNames(), []);

apps/meteor/client/views/admin/settings/Setting/inputs/SelectTimezoneSettingInput.tsx

@@ -1,4 +1,5 @@
 import { Field, FieldHint, FieldLabel, FieldRow, Select } from '@rocket.chat/fuselage';
+import { canonicalizeTimezone } from '@rocket.chat/tools';
 import type { ReactElement } from 'react';
 
 import { useTimezoneNameList } from '../../../../../hooks/useTimezoneNameList';
@@ -38,7 +39,7 @@ function SelectTimezoneSettingInput({
 			<FieldRow>
 				<Select
 					id={_id}
-					value={value}
+					value={typeof value === 'string' ? canonicalizeTimezone(value) : value}
 					placeholder={placeholder}
 					disabled={disabled}
 					readOnly={readonly}

apps/meteor/client/views/omnichannel/businessHours/EditBusinessHours.tsx

@@ -1,6 +1,7 @@
 import type { ILivechatBusinessHour, LivechatBusinessHourTypes, Serialized } from '@rocket.chat/core-typings';
 import { Box, Button, ButtonGroup } from '@rocket.chat/fuselage';
 import { useEffectEvent } from '@rocket.chat/fuselage-hooks';
+import { canonicalizeTimezone } from '@rocket.chat/tools';
 import { Page, PageFooter, PageHeader, PageScrollableContentWithShadow } from '@rocket.chat/ui-client';
 import { useToastMessageDispatch, useTranslation, useRouter, useEndpoint } from '@rocket.chat/ui-contexts';
 import { useId } from 'react';
@@ -14,7 +15,7 @@ import { useRemoveBusinessHour } from './useRemoveBusinessHour';
 
 const getInitialData = (businessHourData: Serialized<ILivechatBusinessHour> | undefined) => ({
 	name: businessHourData?.name || '',
-	timezoneName: businessHourData?.timezone?.name || 'America/Sao_Paulo',
+	timezoneName: canonicalizeTimezone(businessHourData?.timezone?.name || 'America/Sao_Paulo'),
 	daysOpen: (businessHourData?.workHours || defaultWorkHours()).filter(({ open }) => !!open).map(({ day }) => day),
 	daysTime: (businessHourData?.workHours || defaultWorkHours())
 		.filter(({ open }) => !!open)

packages/tools/src/timezone.spec.ts

@@ -0,0 +1,29 @@
+import { canonicalizeTimezone } from './timezone';
+
+describe('canonicalizeTimezone', () => {
+	it('returns the same value for a canonical IANA zone', () => {
+		expect(canonicalizeTimezone('America/Sao_Paulo')).toBe('America/Sao_Paulo');
+	});
+
+	it('resolves plain UTC to UTC', () => {
+		expect(canonicalizeTimezone('UTC')).toBe('UTC');
+	});
+
+	it('resolves Etc/UTC and Etc/GMT to UTC', () => {
+		expect(canonicalizeTimezone('Etc/UTC')).toBe('UTC');
+		expect(canonicalizeTimezone('Etc/GMT')).toBe('UTC');
+	});
+
+	it('resolves legacy moment aliases to their canonical zone', () => {
+		expect(canonicalizeTimezone('GMT')).toBe('UTC');
+		expect(canonicalizeTimezone('Zulu')).toBe('UTC');
+		expect(canonicalizeTimezone('Universal')).toBe('UTC');
+		expect(canonicalizeTimezone('US/Pacific')).toBe('America/Los_Angeles');
+		expect(canonicalizeTimezone('Japan')).toBe('Asia/Tokyo');
+	});
+
+	it('returns the input unchanged when it is not a recognized zone', () => {
+		const input = 'Not/A_Zone';
+		expect(canonicalizeTimezone(input)).toBe(input);
+	});
+});

packages/tools/src/timezone.ts

@@ -34,3 +34,11 @@ export const guessTimezoneFromOffset = (offset: string | number): string => {
 };
 
 export const guessTimezone = (): string => new Intl.DateTimeFormat().resolvedOptions().timeZone;
+
+export const canonicalizeTimezone = (name: string): string => {
+	try {
+		return new Intl.DateTimeFormat(undefined, { timeZone: name }).resolvedOptions().timeZone;
+	} catch {
+		return name;
+	}
+};