Time Zones & Date Difference
One moment across eight time zones, plus natural-day, weekday and duration differences.
Remote collaboration starts with time: it is 3 PM in Shanghai — what is that for the New York teammate? A release window "at UTC midnight" lands at what bedtime? This tool anchors on one moment and shows it across UTC and eight major zones at once, each row labeled with its offset, your own zone highlighted. Change the anchor and the whole table follows.
The date-difference calculator reports two conventions on purpose: calendar days (how many midnights you cross — the vacation-day way to count) and precise duration (multiples of 24 hours — the billing way), plus weeks and weekdays in between. Release countdowns, contract deadlines, probation lengths — one page.
There is only one instant; zones are clothing
Both sides of the table share a single instant: set 14:00 in Shanghai and New York flips to its matching early morning — this is not converting between two times, it is displaying one time two ways. That is also the right mental model for systems: store UTC instants in the database, apply zones only at display time.
Calendar days vs 24-hour spans
From Saturday 23:00 to Sunday 01:00 is 2 hours of duration but 1 calendar day. DST switch days are worse: a 23- or 25-hour day counts as exactly 1 calendar day. Showing both conventions side by side spares you the "which one did they mean" reply.
Frequently asked questions
- Are DST transitions handled?
- Yes. Zone rendering uses the browser's built-in IANA database (Intl), which carries current DST rules; the offset column shows the true offset at that instant, not a fixed +8/-5.
- How are weekdays counted?
- Scanning calendar days in your local zone, excluding Saturdays and Sundays. Public holidays are not excluded — regional holiday rules vary, so subtract those separately if needed.
- Can I add more zones?
- The table ships eight zones covering the main collaboration corridors. Any IANA name (like America/Chicago) can be verified with Intl; more zones will be added on demand.