Where is it daytime right now?
Roughly half the planet, always — but which half moves west at a thousand miles an hour, and the shape of it changes with the season.
The short answer
Almost exactly half the earth is in daylight at any moment — and the lit half is centred on wherever local time is currently noon.
To work it out for a place: if its local time is between sunrise and sunset, it is light. As a rough rule, anywhere whose local clock reads between about 06:00 and 18:00 is in daylight, with the margins widening in its summer and narrowing in its winter.
The half-and-half rule
The sun lights one hemisphere at a time. That is a geometric fact and it does not change with the season — what changes is which half, and how the boundary is tilted.
Slightly more than half, in fact. Two small effects push it over: atmospheric refraction bends sunlight around the horizon, and the sun is a disc rather than a point, so its upper edge appears before its centre. Together they add roughly half a degree.
Finding the lit half without a map
The lit half is centred on the meridian where it is currently solar noon. Work backwards from UTC:
- Take the current UTC hour.
- Solar noon is at longitude 180° − (15° × UTC hour).
- Daylight extends roughly 90° either side of that.
At 12:00 UTC, solar noon sits near longitude 0° — the Greenwich meridian — so Europe and Africa are in the middle of their day, the Americas are in morning or still dark, and the Pacific is in night.
At 00:00 UTC it is the mirror image: the Pacific is at midday, Europe is asleep.
The seasonal part
Where the boundary sits at high latitudes depends on the month, and the effect is extreme.
- June: the Arctic is lit around the clock. Northern Scandinavia, Alaska and northern Russia have no true night. Antarctica has no day at all.
- December: exactly reversed.
- March and September: near-equal day and night almost everywhere, because the boundary runs close to pole-to-pole.
Near the equator none of this matters much — day length stays close to twelve hours all year, which is why tropical cities have such stable sunrise times.
Why this is a useful thing to be able to eyeball
If you deal with people in other countries, "is it daytime there?" is usually the question underneath "can I message them now?"
It is a coarser question than "are they working," and coarser again than "are we both free" — but it is the one that stops you sending something at 4am. For the finer version, you want an actual overlap window; see time zone overlap.
Two things that break the intuition
China. One country spanning about five geographic hours of longitude, running on a single official clock. In the far west, the sun can rise when the clock says mid-morning and set late in the evening. The clock is correct; the sun is simply not aligned to it. See China's single time zone.
High-latitude summer. "It is 10pm so it must be dark" fails badly in Stockholm or Anchorage in June, where it is still bright. Local clock time is a poor proxy for daylight above about 50° latitude in the summer months.
Related: Day and night map · The day/night terminator, explained
Timezone: World Clock Widget
A world clock, converter and live day/night map for iPhone — 325 cities, offline, no account.
Figures on this page are computed from the IANA time zone database. Last generated 2026-08-18.