Timezone Converter
Pick a time of day, see it in every city you care about side-by-side. DST-aware via your browser's IANA database. The day-night strip shows at a glance whether you'd be waking someone up.
How it works
The converter uses the browser's built-in Intl.DateTimeFormat,
which ships with the full IANA timezone database (3000+ zones,
historical and current). No external API, no rate limits, no
network requests after page load. DST transitions are tracked
automatically, including the parts of the world (most of the EU,
most of North America, parts of Australasia) that have asymmetric
DST schedules.
The "anchor" time you set is interpreted as today, in your local timezone. The other rows show what the corresponding moment looks like in their own zone — including the date, since "9:00 AM in San Francisco" might be "tomorrow at 1:00 AM in Tokyo."
Why the day-night strip?
A 24-hour gradient (dark blue at night, orange at sunrise/sunset, light during the day) with a marker at the current hour gives an at-a-glance answer to "is this a reasonable time?" without parsing the actual numbers. Especially useful when scheduling across 3+ timezones.
Common workflows
- Schedule a meeting — set the time to "your preferred slot," scan the strip across cities, pick a slot where most are in their day-bands.
- Async DM timing — see if the person you're about to ping is in working hours.
- Travel — what time will it be when you land? Pick your arrival time + your destination zone.
- Live event timing — paste the event time + organizer's zone, see when it fires for your audience.
Related
- Conversion hub
- Date calculator — for date math (days between, countdown)
- Unix epoch converter — for timestamp interchange
- Unit converter — for length, weight, temperature, etc.
FAQ
Is anything I enter sent to a server?
No. The converter uses your browser's built-in Intl.DateTimeFormat, which carries the IANA timezone database. No network request is made when you change the time or add a city.
Does this handle daylight saving time?
Yes — automatically. The browser's IANA tz database tracks DST transitions for every supported zone. If you ask 'what time is it in London at 14:00 EST?' on a date that's between the US and EU DST changeovers (which don't sync), the answer accounts for both.
What's the day-night strip showing?
It's a 24-hour visual hint: dark blue = night, orange = dawn/dusk, yellow = day. The vertical line marks the current hour in that timezone for the time you selected. Useful for 'is this a reasonable time to message someone in Singapore?' at-a-glance.
Why these timezones and not all of them?
The IANA database has 300+ zones. Listing them all is overwhelming and most are duplicates (every zone has the same UTC offset as its neighbors most of the year). We curated ~40 zones covering major business hubs across every continent. Email hello@tooljo.com if you need one we don't have.