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About Whenmap

Whenmap — The map of when. — is a live world time zone map. Every region is coloured by the UTC offset its clocks show right now, so places that share a clock share a colour. Click anywhere for the local time, the next daylight saving change and everyone else on the same clock, or slide time forward to watch the borders move as countries change their clocks.

How the colours work

Each UTC offset has one colour, and neighbouring offsets always look clearly different: the hue turns 63° for every hour, so the 27 whole-hour offsets from UTC−12 to UTC+14 never repeat a colour. Half- and quarter-hour offsets sit between their neighbours.

UTC−5UTC−4UTC+0UTC+1UTC+5:30UTC+5:45UTC+9

Colours follow the clock, not the zone name, and a border is drawn where two neighbouring clocks disagree. In winter Arizona and Colorado both show UTC−7 and share one colour; in March Colorado moves to UTC−6 while Arizona stays put, so its colour changes and the border between them appears — until November, when it disappears again. Solid lines are borders on land; dashed lines run through water.

The time slider

The map can show any moment from shortly before today until about two years ahead — the period its boundaries were built for. Scrub or type a date and time, and every clock, colour and border follows; the moon-blue frame tells you the map is not showing now. Links can carry the moment you are looking at.

Where the data comes from

  • Clock rules: the IANA time zone database (tzdb, public domain), as built into the browser and, for these pages, into the build machine (tzdb 2026d). Rule texts, next changes and offset histories on these pages are computed from it.
  • Zone boundaries: timezone-boundary-builder release 2026b, derived from OpenStreetMap (© OpenStreetMap contributors, ODbL), simplified and corrected by hand where the source is wrong.
  • Sea areas: nautical time bands in the style of the CIA World Factbook time zone map (treyerl/timezones, MIT), so islands sit inside a band of the right colour.
  • Land, countries and US states: Natural Earth (public domain).
  • Cities: GeoNames (CC BY 4.0), about 6,984 places with 100,000 or more people plus capitals; 762 of them have their own page. Each city takes the zone of the map area it lies in.
  • Sunrise and sunset: NOAA’s solar equations (Meeus), good to about a minute between the polar circles.

Accuracy

Governments change their clock rules, sometimes at short notice. The live clocks use your browser’s copy of the tz database and are corrected against a time server; the text on these pages was generated from tzdb 2026d and is refreshed at least monthly and before every March and October clock change. Map boundaries use release 2026b, generated 2026-07-03.

Some tz database zones are not drawn separately: for example Asia/Urumqi, because Xinjiang’s official clocks follow Beijing time. Uninhabited Baker and Howland Islands, which have no tz database zone, are shown on UTC−12.

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