Time Zone Overlap Calculator for Remote Teams

Why a golden meeting window matters for distributed teams

When your team spans New York, London, and Tokyo, there are only a few hours each day when everyone is simultaneously awake and working. This free time zone overlap calculator maps each city's core hours, flexible hours, and sleep hours onto a single UTC timeline, then highlights the golden window — the longest stretch where every participant is in core working hours.

The tool is built entirely on the browser-native Intl.DateTimeFormat API, so daylight saving time transitions in the US, UK, EU, and Australia are calculated automatically from the latest IANA time zone database shipped with your browser. Copy the suggested slot in one click and paste it straight into Slack, Teams, or a calendar invite.

How the golden overlap is calculated

Every city you add is broken down into 96 fifteen-minute slots on a shared UTC axis. Each slot is classified using that city's real local time — not a fixed UTC offset — which is why daylight saving time is handled correctly even on transition days:

• Core working hours (default 09:00–18:00 local) — the best time to schedule a meeting for that participant.
• Flexible hours (default 07:00–09:00 and 18:00–21:00 local) — early birds and overtime; acceptable for smaller or optional meetings.
• Off-hours (default 21:00–07:00 local) — sleep time; the scheduler avoids placing anyone here.

The calculator then scans the whole day for the longest contiguous stretch where every selected city is in core hours. If no such stretch exists, it falls back to the longest window where everyone is at least in flexible hours, and as a last resort it reports the one-hour window with the highest total availability score — a practical compromise when, for example, a San Francisco–London–Singapore call simply cannot work for everyone at once.

Tips for scheduling across time zones

• Rotate the pain. If the only overlap lands outside someone's core hours, alternate which region takes the awkward slot each week instead of always sacrificing the same team.
• Prefer the flexible zone over the graveyard shift. A 08:00 start in London is far better for teamwork than a 23:00 call for your Tokyo colleagues.
• Book around DST transition weeks. US and Europe switch on different dates (roughly March and October/November), so a recurring meeting that worked in winter can drift by an hour in spring. This tool recalculates using today's actual rules, so check the timeline after each transition.
• Watch half-hour time zones. India (UTC+5:30), Nepal (+5:45), and parts of Australia don't align to whole hours — the 15-minute timeline slots handle these precisely.
• Anchor on UTC, communicate in local time. Store the meeting in UTC and always show each participant their own local time — exactly what the result panel and Copy Meeting Slot button do for you.

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Frequently asked questions

How does this tool handle daylight saving time (DST)?

It uses your browser's built-in Intl API with the latest IANA time zone database, so every calculation automatically reflects current DST rules for each city — no manual adjustments needed, even on the day clocks change.

How many cities can I compare at once?

You can add between 2 and 5 cities and instantly see their working hours, flexible hours, sleep hours, and the golden overlap window where everyone is available. The database covers 120+ major business and digital-nomad cities across every continent.

Is any data sent to a server?

No. All calculations run locally in your browser. There is no backend, no account, and no tracking of your selections — the page works even offline once loaded.

Why does it sometimes show a "best compromise" instead of a golden window?

Some city combinations — like Los Angeles, Berlin, and Sydney — genuinely share no waking hours. When that happens, the tool surfaces the window with the highest combined availability and marks which participants would be outside core hours, so you can decide consciously rather than guessing.

What is a good meeting time for teams across the US and Europe?

For US East Coast and Western Europe, the sweet spot is typically 13:00–17:00 UTC (9:00–13:00 in New York, 14:00–18:00 in London). Add cities above to check the exact window for your team on today's date — it shifts with daylight saving time.