What the world clock shows
The world clock displays the current local time in up to 6 cities simultaneously, updating every second. Each city card shows the time in 24-hour format, the local date (which may differ from your date across the international date line), the UTC offset, and a visual indicator of whether that city is currently in business hours (9am–6pm), outside business hours, or in the middle of the night.
Adding and removing cities
Click the dropdown on any city card to change it to a different city. Click "+ Add city" to add up to 6 total. Click the × button to remove a city. Your city selections are saved in the current session — if you use the world clock regularly, keep it open in a dedicated browser tab for a persistent display that you can glance at throughout the day.
Daylight saving time handling
All times use the browser's Intl.DateTimeFormat API with IANA time zone identifiers, which automatically handles all daylight saving time transitions for all locations. You never need to manually adjust for DST — the clock shows the correct local time in each city regardless of the time of year. This is important because DST transitions happen on different dates in different countries: the US and Canada switch on the second Sunday in March, most of Europe on the last Sunday in March, Australia in April and October, and many countries not at all.
The 24-hour overlap grid
Below the city clocks, the 24-hour grid shows all 24 hours of your local day and what time that corresponds to in each selected city. Green cells indicate business hours (9am–6pm) in that city; dark cells indicate night time (10pm–6am); uncoloured cells are the in-between hours. The current hour row is highlighted in your accent colour. This grid makes it immediately obvious at which local times all or most of your cities are simultaneously available.
UTC reference
The UTC reference bar at the bottom shows the current UTC time. All time zones are expressed as offsets from UTC — knowing the UTC time lets you do quick mental arithmetic for any city without needing to add it to the clock. Developers, pilots, naval officers, and anyone doing international scheduling work in UTC natively rather than converting back and forth between local times.