Keep calendar dates as dates

How to do it

In JavaScript, new Date('2026-03-05') means midnight UTC, which shows as 4 March west of UTC. Use Temporal.PlainDate. Firefox 139 and Chrome 144 ship it, but Safari did not in October 2026, so load a polyfill such as @js-temporal/polyfill there. Without it, split the string and format with timeZone: 'UTC'. Send the date input's value string as it is. Store it in a date column, not a timestamp.

Example

import { Temporal } from '@js-temporal/polyfill';

export function formatCalendarDate(value: string, locale: string): string {
  return Temporal.PlainDate.from(value).toLocaleString(locale, { dateStyle: 'long' });
}

export function formatCalendarDateWithoutTemporal(value: string, locale: string): string {
  const [year, month, day] = value.split('-').map(Number);
  return new Intl.DateTimeFormat(locale, { dateStyle: 'long', timeZone: 'UTC' }).format(Date.UTC(year, month - 1, day));
}

from datetime import date
from babel.dates import format_date

due = date.fromisoformat("2026-03-05")
print(format_date(due, "long", locale="en_GB"))

How to check

Run the date tests with TZ=America/Los_Angeles and TZ=Pacific/Auckland. A due date of 2026-03-05 saves and shows as 5 March in both.