About this site

Time Zone History is an independent reference site run by Blake Patterson. It shows, for every zone in the IANA tz database, how its clocks have been set since records begin: the end of local mean time, every change of standard time, every season of daylight saving time, and the clock change dates that follow from the rules in force today.

The site has a page for each of the 154 countries and territories with a clock record of their own, a page for each zone in countries that have several, and a converter that works on any date from 1900 to 2037 using the same records.

Where the data comes from

Everything on the site is computed from the IANA Time Zone Database (also called tz, tzdata or zoneinfo), release 2026f, published on 2026-10-27. The database is maintained by a community of volunteers and published by the Internet Assigned Numbers Authority at iana.org/time-zones. It is in the public domain. This site is not affiliated with IANA or with the database’s maintainers, and the commentary in the database files is not reproduced here; the pages use its facts (offsets, dates, rules, names) and the site’s own calculations.

How each figure is calculated is set out on about the data.

What this site does not do

The site describes what the tz database records. It does not give legal, travel or scheduling advice, and it is not an official source for the time in any country. Governments set their own clocks, sometimes at short notice; for anything that matters, check the official announcement of the country concerned.

Contact

Corrections and questions are welcome at support@timezonehistory.online. If the database itself is wrong, the right place to report it is the tz mailing list described on the IANA page above.