Time zone overlap calculator
See the hours your whole team is working at the same time on a real date, with daylight saving applied. Then see who can cover when someone is out.
How do you find overlapping work hours across time zones?
Put everyone's working hours on one clock, then take the latest start and the earliest end. If the latest start comes before the earliest end, that window is your shared time. New York and London on 9:00 to 17:00 share 3 hours for most of the year (14:00 to 17:00 London time), and 4 hours in the weeks when only one of them has changed its clocks.
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Worked example: San Francisco, New York and London
On Tuesday, October 27, 2026, with everyone on 9:00 to 17:00, the three cities share 1 hour: 9:00 to 10:00 in San Francisco, 12:00 to 13:00 in New York and 16:00 to 17:00 in London. London has already moved its clocks back (October 25) and the US has not (November 1), so this week London is 4 hours ahead of New York instead of 5.
| Time zone | If they’re out, someone else is working | Best cover |
|---|---|---|
| San Francisco | 5 of 8 hours | New York |
| New York | 8 of 8 hours | San Francisco |
| London | 4 of 8 hours | New York |
When London is out, nobody else is working for its first four hours, 9:00 to 13:00. Anything urgent in that window needs a named person who agrees to start early, or it waits.
Why the overlap changes during the year
Countries change their clocks on different dates, and many never change them. In 2026, the US moved its clocks forward on March 8 and back on November 1. The UK and the EU moved forward on March 29 and back on October 25. Sydney moved back on April 5 and forward on October 4. India, Japan and most of Arizona do not change their clocks at all.
So for about three weeks in March and one week around the start of November, US and European teams are an hour closer than usual. Pick the date you are planning for, not today, when you book a recurring meeting.
How much overlap does a remote team need?
There is no standard number. Use the shared window for the work that needs a live conversation: decisions, unblocking and handing over. Move the rest to writing. With less than an hour or two, plan handoffs in writing at the end of each day, and agree who answers urgent questions in the hours nobody shares.
Who covers when someone is out?
The table counts how many of each person’s working hours someone else is also working. That is the most cover the team can give while they are away. The best cover is the teammate who shares the most hours with them. It is a starting point: they still need the context, the access and the time.
Write it down before the time off starts. The vacation coverage plan template lists each responsibility with its covering owner and escalation contact, and the team coverage planner checks whether enough people are left on a given day.
What this calculator does not know
It does not know public holidays, part-time schedules or who is already on leave. For holidays, check public holidays 2027 by country for each teammate’s country. Add those to your team vacation calendar and check the dates there. Working hours are the ones you enter; it does not read calendars.