About worldclock.tools

worldclock.tools is a set of 36 free tools for working with time across places: live world clocks, meeting planners, time zone converters, timers, and a group of developer utilities for the timestamp formats that show up in logs and APIs. Alongside them are local-time pages for 34,043 cities across 244 countries and territories.

Everything is free to use. There is no account, no sign-up, no paywall, no advertising and no tracking. There is no premium tier being held back, and nothing here is a trial for something else.

Time zone mistakes are unusually costly relative to how ordinary they are. A meeting an hour off, a deploy that fires during a skipped hour, a deadline interpreted in the wrong zone — each is a small error with a disproportionate cost, and each comes from the same root cause: people reason about offsets as if they were fixed, when they are functions of a date and a government's current policy.

Most of the tools that exist to prevent this are surprisingly poor. They load slowly, carry more advertising than content, and a disappointing number get daylight saving wrong at exactly the moments it matters — the weeks in spring and autumn when two regions have not yet both changed their clocks. This site is an attempt to do the same job carefully and quickly.

Every calculation runs in your browser. Time zone rules come from the IANA time zone database that ships inside your browser and operating system, which is the authoritative source that essentially all software uses. Because the rules are evaluated locally for the specific date in question, daylight saving is handled correctly for each zone independently — including the awkward weeks when regions are out of step.

What you enter is never transmitted. There is no geolocation prompt, no analytics, no tracking cookie, and no server-side copy of anything you type into a tool. Boards and preferences are kept in your browser's local storage and stay on your device. The only request carrying anything you typed is city search, which sends the letters and nothing else. The privacy policy sets this out in full.

A practical side effect is that the tools work offline. Once a page has loaded, the rules it needs are already present, so clocks keep ticking and converters keep converting without a connection.

Time zone rulescome from the IANA time zone database (also called tzdata or the Olson database), by way of your browser's built-in internationalisation support. It is updated several times a year as governments change their rules, and keeping your browser and operating system current is what keeps these results accurate.

City data — names, countries, administrative regions, coordinates and time zone assignments — comes from GeoNames, used under the Creative Commons Attribution 4.0 licence. Sun, moon and solar-position figures are computed from standard astronomical algorithms using each city's real coordinates.

Clocks here are only as accurate as the device they run on. If your computer's clock is out by a minute, so is every reading on this site — the page does not contact a time server to correct for that. Enabling automatic network time on your device is the fix.

Sunrise and sunset are computed for sea level and a flat horizon, and can differ by a minute or two from what you observe from a hill or a valley. Astronomical figures are intended for planning rather than navigation. Market hours reflect regular sessions and do not account for national holidays or half-days.

If something looks wrong, please say so — corrections are welcome and usually quick to make. The contact page has the address.

Questions, corrections, or a tool you wish existed: contact@worldclock.tools.