A time zone is more than an offset from UTC. Arizona keeps Mountain Standard Time all year while its neighbours change their clocks, Indiana is split between two zones, Nepal is 5 hours 45 minutes ahead of UTC, and China uses a single zone across five geographical ones. Computers therefore name zones after a city in the IANA tz database, such as America/Phoenix or Asia/Kathmandu, and each name carries the full history of the area's clock changes. This tool shows the boundaries of all 419 IANA zones on a map, coloured by their offset from UTC. Click anywhere, search for a town or use your location, and the zone is filled in green while every zone with the same time right now turns light green. The panel gives the zone's name, the local time ticking by the second, the UTC offset, whether daylight saving time is in force and when the clocks next go forward or back, how far the place is ahead of or behind your own clock, when the sun is highest there, and how far you are from the nearest zone boundary. Add places to the comparison list to see the time in several cities at once, choose any date and time in the first place to plan a call or a flight, and download the list as CSV or the zone outline as GeoJSON or KML.
How to use it
- Press "Use my location", search a town or city, paste coordinates or click anywhere on the map.
- Read the time zone, local time, UTC offset and the next clock change in the panel.
- Press "Add to the comparison" for each place you want to compare, and pick a date and time in the first place to see the time everywhere else.
- Download the comparison as CSV or the zone outline as GeoJSON or KML, or copy the share link.
How accurate is it?
Where the zone boundaries come from
The boundaries are those of timezone-boundary-builder, a project that builds every IANA time zone from country and province borders in OpenStreetMap, including territorial waters out to 12 nautical miles. To load the whole world in a browser they are simplified to about 4 % of their points. We tested the result against the full-detail boundaries: on 40,000 random points on land, 99.96 % fell in the same zone, and every point that did not was within 0.7 km of a boundary. For the 24,323 towns and cities in our place list, the UTC offsets agreed in 99.95 % of cases. Within 1 km of a boundary the tool warns you and names the zone on the other side.
Where the clock rules come from
The offset, the daylight saving rules and the dates of clock changes are not stored by GeoDrafter. Your browser has its own copy of the IANA tz database, the same one phones and servers use, and the tool asks it through the standard Intl interface. When a country changes its rules, the times here are right as soon as your browser has been updated. Clock changes are found by checking the offset day by day for the next 400 days and then narrowing down to the exact second.
Solar noon and the sun
Solar noon, the moment the sun is highest, is worked out from the longitude and the equation of time (NOAA's approximation, good to about a minute). It shows how far the legal clock is from the sun: in western Spain or western China the sun is highest after 14:00 in summer, because the clocks follow a zone far to the east.
Good to know
Disputed areas and local custom
In a few places two zones are in use: in Abkhazia and some other disputed areas each side keeps its own time, and in Xinjiang many people use Ürümqi time two hours behind official Beijing time. The tool then names both zones and gives the time in each. Which one applies to you depends on whom you ask.
Abbreviations are ambiguous
CST can mean Central Standard Time in North America, China Standard Time or Cuba Standard Time, and IST is used in India, Ireland and Israel. That is why the tool gives the IANA name and the UTC offset, which are unambiguous, and the zone's long name in your language from your browser.
At sea and near the poles
Out at sea no country's law applies. The tool gives the nautical time zone, a band 15° of longitude wide named like Etc/GMT+2 (the sign is reversed by an old POSIX convention: Etc/GMT+2 is UTC−2). Ships often keep the time of their home port instead. Research stations in Antarctica each choose their own time.
Frequently asked questions
What time zone am I in right now?
Press "Use my location" and allow your browser to share its position. The tool shows the IANA time zone, the local time and the UTC offset. Your position stays in your browser and is never sent to GeoDrafter.
What is the difference between a time zone and a UTC offset?
A UTC offset such as UTC+01:00 is how far the clock is from Coordinated Universal Time at one moment. A time zone such as Europe/Paris is a region whose clocks have followed the same rules, including when the offset changes for summer time. Denver and Phoenix share an offset in winter, but they are separate zones, because Denver changes to summer time and Phoenix does not.
When do the clocks change?
Click the place and read "Next clock change" in the panel. In the European Union the clocks go back on the last Sunday of October and forward on the last Sunday of March; in the United States and Canada they go back on the first Sunday of November and forward on the second Sunday of March. Most of Asia, Africa and South America do not change their clocks at all.
How do I convert a time between time zones?
Add the places to the comparison list and pick a date and time in the first place. Every other place in the list shows its local time at that same moment, with the difference in hours, taking daylight saving time on that date into account.
Why is the time zone different from what my phone says?
Phones near a zone boundary sometimes pick up a mobile mast on the other side and switch zones. Your phone may also be set to a fixed zone. The tool uses the place on the map, so check that the point is where you are and how far it is from the nearest boundary.
Something wrong or missing? E-mail [email protected] and it will be fixed.