fix(settings): display birthday correctly regardless of browsers timezone

apps/settings/src/components/PersonalInfo/BirthdaySection.spec.js

@@ -0,0 +1,106 @@
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { mount } from '@vue/test-utils'
+import timezoneMock from 'timezone-mock'
+import { afterEach, describe, expect, it, vi } from 'vitest'
+
+let personalInfoParameters
+vi.mock('@nextcloud/initial-state', () => ({
+	loadState(app, key, fallback) {
+		if (app === 'settings' && key === 'personalInfoParameters' && personalInfoParameters !== undefined) {
+			return personalInfoParameters
+		}
+		if (fallback !== undefined) {
+			return fallback
+		}
+
+		console.error('Unexpected loadState call without fallback', { app, key })
+		throw new Error()
+	},
+}))
+
+const savePrimaryAccountProperty = vi.hoisted(() => vi.fn())
+vi.mock('../../service/PersonalInfo/PersonalInfoService.js', () => ({
+	savePrimaryAccountProperty,
+}))
+
+async function mountBirthdaySection() {
+	const BirthdaySection = await import('./BirthdaySection.vue')
+	return mount(BirthdaySection.default, {
+		mocks: {
+			t: (_app, text) => text,
+		},
+	})
+}
+
+afterEach(() => {
+	timezoneMock.unregister()
+	personalInfoParameters = undefined
+	vi.resetModules()
+})
+
+describe('BirthdaySection', () => {
+	it('saves value', async () => {
+		personalInfoParameters = {
+			birthdate: {
+				name: 'birthdate',
+				value: null,
+			},
+		}
+		savePrimaryAccountProperty.mockReturnValue(Promise.resolve({
+			ocs: { meta: { status: 'ok' } },
+		}))
+		const wrapper = await mountBirthdaySection()
+
+		const input = wrapper.find('input')
+		await input.setValue('1987-12-01')
+
+		await expect.poll(() => savePrimaryAccountProperty.mock.calls.length).toBe(1)
+		expect(savePrimaryAccountProperty).toHaveBeenCalledWith(
+			'birthdate',
+			'1987-12-01T00:00:00.000Z',
+		)
+		expect(input.element.value).toBe('1987-12-01')
+	})
+
+	it('displays value when browser timezone is set', async () => {
+		timezoneMock.register('US/Pacific')
+		personalInfoParameters = {
+			birthdate: {
+				name: 'birthdate',
+				value: '1987-12-15T00:00:00.000Z',
+			},
+		}
+
+		const wrapper = await mountBirthdaySection()
+
+		expect(wrapper.find('input').element.value).toBe('1987-12-15')
+	})
+
+	it('saves value when browser timezone is set', async () => {
+		timezoneMock.register('US/Pacific')
+		personalInfoParameters = {
+			birthdate: {
+				name: 'birthdate',
+				value: null,
+			},
+		}
+		savePrimaryAccountProperty.mockReturnValue(Promise.resolve({
+			ocs: { meta: { status: 'ok' } },
+		}))
+		const wrapper = await mountBirthdaySection()
+
+		const input = wrapper.find('input')
+		await input.setValue('1987-12-01')
+
+		await expect.poll(() => savePrimaryAccountProperty.mock.calls.length).toBe(1)
+		expect(savePrimaryAccountProperty).toHaveBeenCalledWith(
+			'birthdate',
+			'1987-12-01T00:00:00.000Z',
+		)
+		expect(input.element.value).toBe('1987-12-01')
+	})
+})

apps/settings/src/components/PersonalInfo/BirthdaySection.vue

@@ -13,7 +13,7 @@
 			:id="inputId"
 			type="date"
 			label=""
-			:model-value="value"
+			:model-value="timezoneAdjustedValue"
 			@input="onInput" />
 
 		<p class="property__helper-text-message">
@@ -33,6 +33,16 @@ import { handleError } from '../../utils/handlers.js'
 
 const { birthdate } = loadState('settings', 'personalInfoParameters', {})
 
+/**
+ * Convert a birthdate string value into a Date.
+ *
+ * @param {string } birthdateValue - e.g. "1987-12-01" or "1987-12-01T00:00:00.000Z"
+ * @return {Date}
+ */
+function birthdateValueToDate(birthdateValue) {
+	return new Date(birthdateValue)
+}
+
 export default {
 	name: 'BirthdaySection',
 
@@ -44,7 +54,7 @@ export default {
 	data() {
 		let initialValue = null
 		if (birthdate.value) {
-			initialValue = new Date(birthdate.value)
+			initialValue = birthdateValueToDate(birthdate.value)
 		}
 
 		return {
@@ -64,22 +74,38 @@ export default {
 
 		value: {
 			get() {
-				return new Date(this.birthdate.value)
+				return birthdateValueToDate(this.birthdate.value)
 			},
+		},
 
-			/** @param {Date} value The date to set */
-			set(value) {
-				const day = value.getDate().toString().padStart(2, '0')
-				const month = (value.getMonth() + 1).toString().padStart(2, '0')
-				const year = value.getFullYear()
-				this.birthdate.value = `${year}-${month}-${day}`
+		/**
+		 * Adjusted value for usage with `NcDateTimePickerNative` (internally `<input="date">`)
+		 * The saved value is is UTC and we want to show it the same regardless of the browsers/OSs timezone.
+		 * When the adjusted value is displayed and the users timezone is applied, this adjusted value then looks like the UTC value.
+		 */
+		timezoneAdjustedValue: {
+			get() {
+				// example: this.birthdate.value === '1987-12-01T00:00:00.000Z' or '1987-12-01'
+
+				// example: Mon Nov 30 1987 16:00:00 GMT-0800 (Pacific Standard Time)
+				// `NcDateTimePickerNative` would show this as 11/30/1987
+				const date = this.value
+				const timezoneOffsetMilliseconds = date.getTimezoneOffset() * 60 * 1000
+				const adjustedDate = new Date(date.getTime() + timezoneOffsetMilliseconds)
+
+				// example: Tue Dec 01 1987 00:00:00 GMT-0800 (Pacific Standard Time)
+				// `NcDateTimePickerNative` will show this as 12/01/1987
+				return adjustedDate
 			},
 		},
 	},
 
 	methods: {
 		onInput(e) {
-			this.value = e
+			const day = e.getDate().toString().padStart(2, '0')
+			const month = (e.getMonth() + 1).toString().padStart(2, '0')
+			const year = e.getFullYear()
+			this.birthdate.value = `${year}-${month}-${day}`
 			this.debouncePropertyChange(this.value)
 		},
 
@@ -91,7 +117,7 @@ export default {
 			try {
 				const responseData = await savePrimaryAccountProperty(
 					this.birthdate.name,
-					value,
+					value.toISOString(),
 				)
 				this.handleResponse({
 					value,

package.json

@@ -103,6 +103,7 @@
     "msw": "^2.14.6",
     "sass": "^1.100.0",
     "stylelint": "^17.12.0",
+    "timezone-mock": "^1.4.3",
     "vite": "^7.3.5",
     "vitest": "^4.1.4"
   },