Time Coordinator
Pick a date, set each participant's IANA time zone and working hours, and this page finds every shared window when everyone is available. It uses your browser's built-in time-zone engine, so daylight-saving changes are handled correctly for any date.
Plan a day
Shared windows
Zone working windows
| Zone | Local window | Same window in UTC |
|---|
How the overlap is calculated
Every IANA time zone — such as Asia/Riyadh or
America/New_York — is a named region with rules for its
local time, including daylight-saving transitions. The page converts
each zone's working window on your chosen date into UTC minute by
minute, using the browser's Intl engine, then keeps only
the minutes where every zone is in its window. The remaining
contiguous blocks are your shared windows.
Because the conversion happens for the exact date you pick, the result automatically reflects whether a zone is on standard time or daylight saving time that day — and even handles the strange days when a local hour happens twice (fall back) or not at all (spring forward).
For example, someone in Riyadh (UTC+3) working 09:00–17:00 is available 06:00–14:00 UTC, while someone in New York working the same local hours is available 13:00–21:00 UTC in summer but 14:00–22:00 UTC in winter. The page shows you the actual intersection for the date you choose.
When do you need to coordinate across time zones?
A shared-window calculator is useful in a handful of everyday situations where the calendar apps fall short:
- Distributed team rituals. Standups, retros, and planning sessions for teams spread across cities or countries. Finding the daily window where everyone is actually working is the first step to a schedule people can keep.
- Client and partner calls. Freelancers and agencies booking calls with clients abroad often have only a narrow shared window — knowing exactly which minutes overlap (not “roughly morning for them”) is what makes the invite stick.
- Events and launches. Webinars, product launches, and AMAs for audiences in several zones: pick the window where the most people are online, and publish the local time for each region without arithmetic mistakes.
- Support and on-call handovers. Ops and support teams passing shifts between regions need a clean overlap for the handover itself. A fairness rotation across zones is on the roadmap; the shared-window math is the foundation it will use.
A worked example, step by step
Say you work 09:00–17:00 in Riyadh and need to meet colleagues in London and New York on 2026-07-15 (a summer date). Each zone's window, converted to UTC, is:
| Zone | Local window | Same window in UTC |
|---|---|---|
| Asia/Riyadh | 09:00–17:00 | 06:00–14:00 |
| Europe/London | 09:00–17:00 | 08:00–16:00 |
| America/New_York | 09:00–17:00 | 13:00–21:00 |
The only hour when all three are working is 13:00–14:00 UTC — a 1h 0m window. That is 16:00–17:00 in Riyadh, 14:00–15:00 in London, and 09:00–10:00 in New York. Type those zones and hours into the form above with the date 2026-07-15 and you will get exactly this result — then Copy schedule to share it with the exact local times for everyone.
Frequently asked questions
What does “time zone overlap” mean?
An overlap is the block of time when every participant's working window is open at the same moment. If you work 09:00–17:00 in Riyadh and a colleague works 09:00–17:00 in London, your windows overlap from 09:00–14:00 UTC on most dates — and the page tells you exactly which minutes are shared, expressed in everyone's local time.
Is daylight saving time handled automatically?
Yes. The page converts every zone using the browser's built-in time-zone engine for the exact date you pick, so summer and winter offsets come out right without any manual table. On transition days the page also warns you: for example, 2026-03-29 is the UK spring-forward day, and London changes offset overnight.
Can I compare more than two time zones?
Yes — add up to five zones and give each one its working hours. A window only appears in the results when every single zone is inside its working window, so adding more people makes the shared block smaller. Remove a zone with the Remove button if you want to widen the window again.
Why does the same schedule give a different overlap on a different date?
Because daylight-saving offsets change by date. Riyadh and London working 09:00–17:00 overlap for 6 hours on 2026-07-15 (London is on summer time) but only 5 hours on 2026-01-15 (London is on winter time). The page always calculates for the exact date in the Date field, so pick the day you actually plan to meet.
Is this really free and private?
Yes. This is a static page with no account and no server: your zones, dates, and hours are processed entirely in this tab, and the copied schedule is plain text generated on your device. Nothing you enter is sent anywhere — the only network request this page can ever make is the optional, consent-based analytics tag, and it never carries your schedule data.
Why doesn't it support overnight or midnight-crossing shifts?
This prototype plans a single date with same-day working windows, so a shift that starts in the evening and ends after midnight (for example 22:00–06:00) is not supported yet. It also does not know about holidays or personal calendars — treat the result as a coordination starting point, not a guarantee.
Privacy and limitations
Privacy. This page makes no network requests with your dates, zones, and working hours are processed entirely in your browser, and the copied schedule is generated locally. There is no account, no telemetry, and no server.
Limitations. This prototype plans a single date with same-day working windows — overnight shifts that cross midnight are not supported yet. Working hours are minute-accurate but the copyable schedule shows hours and minutes, not holidays, shifts, or personal calendars. Zones come from a curated IANA list; if you need a zone that is missing, note it and a free-text zone field can be added. Fairness rotation, share links, and calendar (.ics) export are planned for a later version.
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