Day / night terminator map
Watch daylight sweep across the planet. The shaded half is where the sun has set, the bright dot is where it's directly overhead, and the city markers show who's in daylight right now.
How to use the day / night terminator map
Read the terminator
The curved line dividing light from dark is the terminator — the boundary between the half of Earth in sunlight and the half in darkness. It sweeps westward at roughly 1,600 km/h at the equator.
Find the subsolar point
The marker at the centre of the lit region is the point where the sun is directly overhead. Its latitude drifts between the tropics across the year, which is what produces the seasons.
Check a city against the shadow
City markers sit on their real coordinates, so you can see immediately whether a place is in daylight, in twilight near the edge, or in full night.
Watch it move
The map redraws continuously against your device clock. Leave it open and you can watch the shadow cross a continent over the course of an afternoon.
What the day/night terminator shows
At any instant, exactly half of Earth is lit. The dividing line is not vertical, which surprises people — it tilts by up to 23.4°, because Earth's rotational axis is tilted relative to its orbit. That tilt is the entire reason seasons exist, and the map makes it visible: in June the shadow leaves the Arctic permanently lit and Antarctica permanently dark, and in December the arrangement reverses.
The terminator is also not a hard edge in practice. Twilight extends the lit region by several hundred kilometres, because the atmosphere scatters sunlight from below the horizon. Civil twilight — sun between 0° and −6° — is bright enough to work outside in, which is why sunset and darkness are two different times and why the band near the edge of the shadow matters.
The subsolar point moves west at a steady rate while its latitude wanders north and south over the year. Following it explains a lot of otherwise abstract facts at once: why day length varies more the further you get from the equator, why the tropics are defined where they are, and why the solstices sit where they do in the calendar.
When it comes in handy
Teaching seasons.
Show a class why the tilt of the terminator, not distance from the sun, produces summer and winter.Satellite and radio work.
Grey-line propagation along the terminator is prized by HF operators; the map shows where that line currently runs.Photography planning.
See at a glance which parts of the world are near their golden hour right now.Scheduling with the far side.
Confirm visually that a proposed call lands in someone's daylight and not their small hours.Understanding polar day.
Watch the Arctic or Antarctic sit entirely inside or outside the lit region depending on the month.Ambient dashboard.
Leave it running on a wall screen as a live picture of where your users currently are awake.
Questions & answers
- What is the terminator?
- The moving line between day and night — the edge of sunlight on Earth. Everything on the shaded side of it is currently in darkness.
- What does the bright dot represent?
- The subsolar point: the single spot where the sun is directly overhead at this instant. It tracks along the tropics through the year and sweeps westward as the planet rotates.
- How accurate is it?
- The sun's position is computed from an astronomical model accurate to well under a degree, so the day-night boundary is faithful to within a minute or two of real time.
Related tools
- Live World Clock Dashboard — Track any set of cities side by side, with day and night at a glance.
- Golden Hour Calculator — Plan the shot around the light, anywhere on the map.
- Solar Noon & True Solar Time — When the sun is highest — not what the clock claims.
- Moon Phase Tracker — The lunar calendar and tonight's phase, wherever you are.
- Equinox & Solstice Countdown — The turning points of the year, counted to the second.
- Analog & Digital Multi-City Clocks — Classic dials and crisp readouts for every timezone you follow.