Time Zone Compare

From your browser's own copy of the IANA time zone database, through the standard Intl API. Daylight-saving dates, half-hour and 45-minute offsets and historical changes are as current as your browser; the page downloads nothing. Each zone's time is named as the browser names it (Singapore Standard Time, British Summer Time); the short form before the name (SGT, BST) comes from a fixed list of common ones on this page, and a time without one shows its name alone. CST and IST each stand for more than one time, so they always come with the name, and when two zones in the table share a short form, a note under the table says so.

A time that does not exist in the reference zone (for example 02:30 on the day clocks jump forward) is moved forward past the gap, and a time that happens twice (the day clocks go back) uses the first occurrence; the page says so whenever either applies. The hour grid always shows the 24 wall-clock hours of the reference date.

Before standard time was adopted (Tokyo in 1888, New York in 1883) the database records each city's local mean time, which is not a whole number of minutes: Tokyo is UTC+09:18:59, New York UTC-04:56:02. The page keeps those seconds rather than rounding them, so 12:00 in Tokyo on 1 January 1880 stays 12:00 (02:41:01 UTC); the offset column and the difference show the seconds, and local times are shown to the minute. Dates run from 1 January of the year 1. A zone west of UTC at 00:00 UTC on that day is still on 31 December of the year before, written 0000-12-31 as in ISO 8601 (year 0000 is 1 BC).

Every named zone your browser knows, usually about 420, listed as city and region with the IANA name (in Chinese, under the browser's own Chinese name of the zone). Type part of a city or zone name under Find a city or zone: the list keeps only the zones that fit, the best first, and Enter adds it. Some big cities and countries with a single zone that no zone is named after are found too, such as Beijing (Asia/Shanghai), Mumbai (Asia/Kolkata), San Francisco (America/Los_Angeles) or Japan (Asia/Tokyo). Chinese words find the browser's Chinese name of each zone and some big cities, such as 北京, 东京, 纽约 or 伦敦; any other city is found by its English name. Aliases such as US/Eastern are not listed; use America/New_York.

Yes. Tick Keep these cities in this browser and the cities of the comparison are kept in their order on this device, and the page opens with them next time, the first one as the reference; untick it and what was kept is removed. Copy a link to this comparison gives an address that opens the same cities, in the same order, on the same date in any browser: they are written after the # in the address, and browsers send that part of an address to no server. The link does not carry the time: the page it opens shows the current time of its first city. A page opened from a link leaves the cities kept in its browser as they are.

Once the page has loaded, yes. Nothing is fetched while you compare.

No. The page loads a small script into your browser and every calculation runs on your device. You can check this yourself in the browser's network panel: after the page has loaded there are no upload requests. Of what you enter, one thing is kept, in this browser on this device and nowhere else: the cities of your comparison, in their order, and only once you tick Keep these cities in this browser; untick it and what was kept is removed.

No. These basic tools are free, and nothing you enter is stored on a server. There are no limits set by us.

Of what you open or type, only what you chose to keep: the cities of your comparison, in their order, and only once you tick Keep these cities in this browser; untick it and what was kept is removed. While the tab is open, the tool pages keep a short list of the steps taken in it, in the tab's session storage: the step (page opened, started, succeeded, first success, used again or failed), the tool's name, the time, how many files were used and, for a failure, an error code; never a file name, the contents of a file or your text. It holds at most the latest 200 steps, and the browser deletes it when the tab closes. The page never sends it. Where a Report a problem button is shown, you can attach the last 20 steps to your report; nothing is attached unless you tick that box. In local storage the page keeps only choices you made: a Light or Dark theme until you choose System again, the language you picked with the EN / 中文 switch if it differs from your browser's language, and this tool in your recently used list if you switched that list on at the tools page.