How to use it
- Pick the date. It is the calendar date in the first time zone.
- Set the start and end of the working day. The same hours are used everywhere.
- Enter the time zones, with a name like
Europe/London; the suggestions list helps. Add up to six. - Read the windows: each one shows the same period on every local clock.
How it works
The planner moves through the day of the first time zone in 15-minute steps. For each step it asks the browser’s time zone data what the local time is in every zone, and keeps the step only if it lies inside the working hours everywhere (and, if you leave the weekday option on, on a weekday everywhere). Consecutive steps become one window, and the total is their combined length.
Worked example
On Tuesday 3 November 2026, with work hours 09:00 to 17:00, for New York, London and Berlin: New York is on UTC-5 (US clocks went back on 1 November), London on UTC+0 and Berlin on UTC+1. The only window is 09:00 to 11:00 in New York, 14:00 to 16:00 in London and 15:00 to 17:00 in Berlin, two hours in total.
Tips
- Two zones far apart (for example Los Angeles and Tokyo) may have no overlap at all; shift the work hours for one side.
- The page opens with your own time zone and today’s date after it loads.