Frequently asked questions

Everything about timezones, UTC, summer time and how this site figures out what time it is where you are.

How does this site know my timezone?
Your browser exposes the timezone your device is configured with through the standard Intl API. The page reads that value locally and formats the clock with it. No IP lookup, no account and no server request are needed.
Why is the time shown in my own language?
Your browser also reports your preferred language. The weekday and month names, the date order and the digit style all follow that setting, so a Japanese visitor sees Japanese month names and a Belgian visitor sees Dutch or French ones.
My timezone is wrong. What can I do?
The clock mirrors your device. Check the date and time settings on your computer or phone and make sure automatic timezone detection is enabled. A VPN does not change your device timezone, but some privacy-hardened browsers deliberately report UTC instead of your real zone.
What is UTC?
Coordinated Universal Time is the global reference clock, maintained by atomic clocks around the world. It never observes summer time. Every civil timezone is defined as an offset from UTC, such as UTC+01:00 or UTC−08:00.
What is the difference between UTC and GMT?
In everyday use they refer to the same moment. GMT is a timezone based on the position of the sun at the Greenwich meridian, while UTC is a time standard based on atomic clocks. For scheduling purposes you can treat them as identical.
Why do some timezones have half-hour or quarter-hour offsets?
Timezones are political as much as geographical. India uses a single UTC+05:30 zone for the whole country, Nepal uses UTC+05:45, and parts of Australia use UTC+09:30. These offsets were chosen to fit local solar time better than a whole-hour zone would.
Why does the difference between two cities change during the year?
Because summer time (daylight saving time) start and end dates differ per country. The European Union switches on the last Sunday of March and October, while the United States switches on the second Sunday of March and the first Sunday of November. During those gaps the usual difference shifts by an hour.
Which countries do not use daylight saving time?
Most of Asia, Africa and South America keep a fixed offset all year, as do Iceland, Russia, Japan, India and China. Within the United States, Arizona (except the Navajo Nation) and Hawaii do not shift their clocks.
Why does the site show a name like Europe/Brussels instead of CET?
Abbreviations are ambiguous and change with the season. The IANA identifier (Europe/Brussels) uniquely identifies a region and carries the complete history of its clock rules, which is what software should store when scheduling across borders.
How accurate is the clock?
It is exactly as accurate as your device clock, which on modern phones and computers is synchronised with internet time servers to within a fraction of a second. The page itself adds no delay because it does not fetch time from anywhere.
How does 'Use my location' work, and is it private?
The browser asks for your permission and then hands the page your approximate coordinates. Those coordinates are matched against a city list that is bundled with the page itself and are never transmitted or stored. You can refuse permission and search for a city instead.
Why is a city missing from the search?
The bundled list covers major cities and capitals worldwide so the site stays fast and works offline. If your town is not listed, search for the nearest large city — it will almost always be in the same timezone.
Can I use a 12-hour clock instead of 24-hour?
The main clock uses a 24-hour format for unambiguous reading. The date line follows your locale, so it will match the conventions you are used to.
Does the site work without an internet connection?
Once the page has loaded, all clocks and lookups keep working offline, because every calculation happens in your browser.

Still stuck with a timezone question? Send it to reinout@reinoutvandepitte.com and it may end up on this page.