OneTaskBy Tim King · Updated
Day Night Map
3D Globe with the Terminator for Any Date and Time, Free Online
OneTask is free, with no sign-up, and built by one person.
If this tool saved you time, a coffee helps keep new ones coming.
How the Earth Day And Night Map works
This day night map shows where the sun is up right now. Set a date and a UTC time and this globe lights the half of the Earth that is facing the Sun, draws the terminator between day and night, and marks the subsolar point where the Sun is directly overhead. Drag to turn the globe, press Use current time to see the world as it is right now, and read the solar declination and equation of time in the stats. Everything runs in your browser and saves as a PNG.
Day night map: what the lit side shows
The Sun lights exactly half of the Earth at any instant. The boundary of that half is the terminator, a great circle that tilts with the seasons. At the equinoxes it passes through both poles and every place on Earth gets twelve hours of daylight. In June the circle tips so the Arctic stays lit all day and the Antarctic stays dark; in December the reverse. The yellow line on the globe is that circle, and the yellow dot is the subsolar point, the one spot where the Sun is at the zenith.
Where the numbers come from
The tool computes the Sun's declination and the equation of time from the date using the same low-precision solar model used by most sunrise calculators, accurate to well under a tenth of a degree over the current century. The subsolar latitude equals the declination. The subsolar longitude comes from the UTC time corrected by the equation of time, which is why solar noon at Greenwich is not exactly 12:00 UTC but drifts up to sixteen minutes either side through the year. Both figures appear in the stats, along with the time of solar noon on the prime meridian.
Reading the globe
Coastlines are drawn from a public-domain world outline. The lit side is shaded by a single directional light so the dawn and dusk zones fade gradually, roughly matching civil twilight, with the sharp yellow line marking the geometric terminator. Turn on the grid for latitude and longitude lines every thirty degrees to read positions off the sphere, and use auto-rotate to let the globe turn while the lighting stays fixed to the Sun.
Typical uses
Check whether a colleague on the other side of the world is in daylight before a call, show a class why the poles get six months of night, plan when a satellite pass will be sunlit, or just confirm that the terminator really is a straight vertical line on the equinox. Set the time to the exact minute of a solstice or equinox and compare.
Saving
Download PNG renders the current view at 1080p, 2K or 4K against the dark background. Turn the globe to the region you want, use Fit view to centre it, then save.
FAQ
Why does the lit half not match the terminator line exactly?
The shading fades smoothly because a real sphere lit from one direction gets darker towards the edge of daylight, and the atmosphere scatters light past the geometric edge. The line marks the exact point where the Sun's centre is on the horizon; the softer shading is what a photograph from space would actually show.
Is the time local or UTC?
UTC. Use current time reads your clock and converts it to UTC automatically. To see a local time elsewhere, convert it to UTC first; the tool does not know time zones because the terminator only depends on universal time.
How accurate is the subsolar point?
Within about a tenth of a degree of latitude and a few hundredths of a degree of longitude, which corresponds to a few kilometres on the ground. That is far better than the width of the line drawn on the globe, so for any visual purpose it is exact.
Can I see city lights or clouds?
No. The globe uses a plain coastline map so that it works offline and loads instantly. Nothing is fetched from any server after the page has loaded, and nothing you enter is sent anywhere.
See also: all 3D Science tools, Images, Audio, Video & Screen, PDF, SVG, Simulations & Screensavers, Generative Art, Chart Makers, 3D Model Viewers, Drawing Pads, Mockups & 3D Making, Diagram Makers, Tracker Music.
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