Timezone Overlap Matrix
Add every city on your team and see, hour by hour, which slots fall inside everyone’s working day. Offsets are resolved from the IANA time zone database for the exact date you pick, so daylight saving is handled rather than guessed — which matters most in March and October, when regions change on different days.
- Price:
- Free, no sign-up
- Data:
- Processed locally
- Reviewed:
Interactive timezone matrix
Team and hours
Input DataAdd at least one location.
No locations selected
Search above and add each teammate's city.
What time works for a meeting across time zones?
Green columns are inside every participant’s working hours; amber means at least one person is stretching. San Francisco, London and Bengaluru overlap around 15:00–17:00 UTC. Always check the specific date: daylight saving transitions land on different days in different regions and move the overlap by an hour for weeks at a time.
How to use the timezone matrix
- Add locations: Search for each teammate city and add them to the grid.
- Set working hours: Define what counts as a reasonable hour for the team.
- Read the matrix: Green columns work for everyone; amber is a stretch; grey is someone night.
- Share the slot: Copy a chosen time with the local hour spelled out for each zone.
How the timezone matrix works
Why time zone maths is harder than it looks
Offsets are not properties of places; they are properties of places at a moment. Arizona does not observe DST while the rest of Mountain Time does. Lord Howe Island shifts by 30 minutes. Several countries have changed their rules in the last decade. The only correct approach is to ask the IANA database what a given zone offset was on a given instant, which is exactly what Intl.DateTimeFormat with a timeZone option does.
How the grid is built
The tool takes 24 UTC instants for the selected date, formats each one in every selected zone, and classifies the resulting local hour against the working window. A column is green only when every participant is inside their window, amber when everyone is at least awake, and grey otherwise.
Practical scheduling advice
- Anchor recurring meetings to a single zone so DST moves them once for everyone, rather than splitting the team.
- Write invitations with the zone spelled out — 15:00 UTC is unambiguous, 3pm is not.
- Rotate unavoidable unsociable slots. A meeting that is always 6am for Sydney is a retention problem.
Timezone Matrix — frequently asked questions
Yes, automatically. The tool uses the IANA time zone database through your browser Intl API, so offsets are computed for the specific date you select. This matters in March and October, when the US, Europe and the southern hemisphere change on different dates and overlaps shift by an hour for weeks.
Some spreads genuinely have none — San Francisco, Berlin and Sydney is the classic example. Widen working hours slightly, look at amber columns, or accept that one person rotates into an early or late call and share the pain fairly across the team.
Yes. Change the date and the whole grid recomputes for that day offsets, which is how you avoid scheduling a recurring meeting that quietly breaks after a DST transition.
No — it covers hours, not calendars. A slot that looks perfect may still land on a national holiday somewhere on your team, so check local holidays before locking in anything recurring.
Official resources & government references
Verified references, primary standards specifications, and official publications governing the rules and calculations implemented in this tool:
IANA Time Zone Database (tzdb)
The authoritative global database of historical and future time zones, daylight saving transitions, and leap seconds.
ISO 8601: Representation of Dates and Times
The international standard for unambiguous calendar date representations and UTC timestamp offsets.
Important Disclaimer
Time zone offsets, local hours, and daylight saving transitions are resolved via your operating system and browser IANA time zone database. Double-check schedules for jurisdictions with unscheduled holiday or regional calendar rules.