World clock
Thirty cities, one screen, ticking every second — with the date and offset so a meeting time is never a guess.
How World Clock works
Dates are computed from your device's clock and timezone settings, both of which stay on the device. Nothing about when you opened the page is reported. Daylight-saving rules come from your browser's own database, so the conversion follows your region rather than a server's guess.
That is the whole architecture: static files, one script, no upload endpoint to leak or log. Close the tab and the work is gone.
How the time is calculated
Each clock is formatted with Intl.DateTimeFormat and an IANA zone name such as Asia/Karachi. The browser already ships the full time zone database, including the daylight-saving rules and their historical changes, so no server is involved and the clocks keep working offline.
The UTC offset shown under each city is read from the same API (shortOffset), which means Dubai always reads +04:00 and London switches between +00:00 and +01:00 on its own dates rather than on a guess.
Reading a clock grid properly
A time alone is not enough to schedule across zones. Three details make the difference: the date (Tuesday in Karachi can still be Monday in Los Angeles), the offset (which changes twice a year in most of Europe and North America), and whether the other person is asleep.
That is what the day/night marker is for. A 09:00 meeting is reasonable; 03:00 is not, and the shading makes that obvious before you send the invite.
| Use | What to look at |
|---|---|
| Booking a call | Time plus day/night marker |
| Sending a deadline | Date, not just the clock |
| Checking a release window | UTC offset of each city |
Why the list is fixed
Thirty cities cover every continent and most business hubs, and a fixed list keeps the page instant — no geolocation prompt, no API call, no layout shift when data arrives. The filter searches both city names and zone names, so typing 'Europe' shows the European cities at once.
Your own zone is selectable at the top, which is useful when you travel and the device has not caught up yet.
Good to know
- Works offline once loaded, including on flights and in locked-down networks.
- No file size limit beyond your device's own memory.
- Free to use, with no account and no usage counter.
- Results are produced locally, so they are not logged or shared with anyone.
Questions
Does it handle daylight saving?
Yes. Times come from the browser's IANA time zone database, which knows the DST rules for each zone and switches them on the right date.
Can I see a city that is not listed?
The list covers thirty cities across every continent. Filtering searches both the city name and the zone name.
Does it need internet?
No. Once the page has loaded the clocks run from the device clock and the local zone database.
Is the time exact?
It matches your device clock to the second. If your device is a few seconds off, so are the clocks.
Time and date tools
Keep going
More time tools
Countdown Timer
Set a countdown in hours, minutes and seconds with a display you can read across the room, a beep at zero, and the remaining time in the tab title.
Open toolBusiness Days Calculator
Count the working days between two dates, skip weekends and a list of public holidays, and choose a five or six day working week.
Open toolMeeting Planner
Pick the cities and the day: one grid shows every hour in every zone, with working hours shaded and the rows where everyone is available outlined.
Open toolWeek Number Calculator
Pick a date and get its ISO week number, ISO year, day of the year, quarter and the Monday-to-Sunday span of that week.
Open toolTimestamp Converter
Convert Unix timestamps to human-readable dates and back, in UTC and your local timezone.
Open toolAge Calculator
Calculate exact age from a date of birth in years, months and days, plus a countdown to the next birthday.
Open tool