Submit dates and times with an explicit time zone

Problem

A date or appointment moves by a day or hour when users and servers use different time zones.

Before you start

Decide whether each value is a calendar date, a local wall-clock time, or an exact instant. These are different domain values and need different storage rules.

Send the local value and zone together

<form ng-post="/api/appointments" on-error="errors = $res">
  <label>
    Local start
    <input name="localStart" type="datetime-local" required />
  </label>
  <label>
    Time zone
    <select name="timeZone" required>
      <option value="Europe/Riga">Europe/Riga</option>
    </select>
  </label>
  <p ng-if="errors.localStart">{{ errors.localStart }}</p>
  <button type="submit">Schedule</button>
</form>

Server contract

Resolve local time with an IANA zone, reject nonexistent daylight-saving times, and define how ambiguous times are chosen. Store exact instants in UTC while retaining the zone when future local scheduling depends on it.

Failure path

Do not append Z to a local value or assume the server’s zone. Return 422 when the local time cannot identify the intended instant.

Apply it now

Classify every date field in one workflow as date, local time, or instant. Rename ambiguous fields and include the missing zone where required.

Verify

Test users in two zones, both daylight-saving transitions, leap day, midnight, and a date-only value that must never shift.