fix: ensure dates are parsed timezone agnostically

Closes #1223

packages/form-js-viewer/package.json

@@ -55,6 +55,7 @@
  "flatpickr": "^4.6.13",
  "ids": "^1.0.5",
  "lodash": "^4.17.21",
+ "luxon": "^3.5.0",
  "marked": "^13.0.0",
  "min-dash": "^4.2.1",
  "preact": "^10.5.14"

packages/form-js-viewer/src/render/components/form-fields/Datetime.js

@@ -1,4 +1,5 @@
 import { useCallback, useContext, useMemo, useState, useEffect, useRef } from 'preact/hooks';
+import { DateTime as LuxonDateTime } from 'luxon';
 
 import classNames from 'classnames';
 
@@ -86,7 +87,7 @@ export function Datetime(props) {
 
  switch (subtype) {
  case DATETIME_SUBTYPES.DATE: {
- date = new Date(Date.parse(value));
+ date = typeof value === 'string' ? LuxonDateTime.fromISO(value).toJSDate() : new Date(NaN);
  break;
  }
  case DATETIME_SUBTYPES.TIME: {

packages/form-js-viewer/src/render/components/util/dateTimeUtil.js

@@ -1,5 +1,6 @@
 import { isNumber } from 'min-dash';
 import { MINUTES_IN_DAY, TIME_SERIALISING_FORMATS } from '../../../util/constants/DatetimeConstants';
+import { DateTime as LuxonDateTime } from 'luxon';
 
 export const ENTER_KEYDOWN_EVENT = new KeyboardEvent('keydown', {
  code: 'Enter',
@@ -145,18 +146,15 @@ export function parseIsoTime(isoTimeString) {
  }
 }
 
+/**
+ * Returns the date object as a simple 'YYYY-MM-DD' formatted date in the local timezone.
+ *
+ * @param {*} date The date object to serialize.
+ * @returns {string} The serialized date.
+ */
 export function serializeDate(date) {
- var d = new Date(date),
- month = '' + (d.getMonth() + 1),
- day = '' + d.getDate(),
- year = d.getFullYear();
-
- if (month.length < 2) month = '0' + month;
- if (day.length < 2) day = '0' + day;
-
- return [year, month, day].join('-');
+ return LuxonDateTime.fromJSDate(date).toISODate();
 }
-
 // this method is used to make the `new Date(value)` parsing behavior stricter
 export function isDateTimeInputInformationSufficient(value) {
  if (!value || typeof value !== 'string') return false;