Time Zone Overlap Calculator
Each person has a time zone and a working window. The page converts those windows on the date you pick and shows the overlap in every local clock. Offsets come from the time zone database for that date, so daylight saving is handled by the date rather than a fixed number of hours.
Calculator
How the number is produced
Convert each local start and end to an absolute instant for the chosen date. The overlap starts at the latest start and ends at the earliest end. If that end is not after the start, there is no shared working time.
Worked example
On 15 January 2026, London 09:00 to 17:00 and New York 09:00 to 17:00 overlap for 3 hours: 14:00 to 17:00 in London and 09:00 to 12:00 in New York.
When this is useful
A team is spread across cities and “afternoon your time” has stopped meaning anything.
Limits
Working hours that cross midnight are treated as ending the next day. The list of cities is a useful set, not every zone on earth. Results depend on the date because clocks change.
More on the assumptions is on how the calculators work.
Questions
Why do you ask for a date?
London and New York are not a fixed number of hours apart all year. The date picks the right offset.
Related tools
If a result disagrees with the formula on this page, email hello@gettowork.online.