Live World Day & Night Map
The shaded half of the map below is currently in night — calculated live from the sun's actual position, not a fixed image. It updates automatically as the Earth turns.
Map time: --:-- UTC
How This Is Calculated
Every point on Earth where the sun is below the horizon is shaded. That boundary — the "terminator" — is computed from two live values: the sun's declination (how far north or south of the equator it's directly overhead, which shifts through the year) and the subsolar longitude (which line of longitude currently has the sun at solar noon, which sweeps 15° every hour as the Earth rotates). The 35 highlighted cities are the ones featured across DateTimeX — click any dot to jump to that city's live clock. For more on why the sun's position maps to timezones at all, see our History of UTC article.
Frequently Asked Questions
Why is the day/night boundary a curve instead of a straight line?
The terminator is a great circle in 3D space, but the map is a flat rectangular
projection of a sphere — that's what turns a straight circular boundary into the
curved line you see. Around the equinoxes (March and September) the sun sits almost
directly over the equator, flattening the curve close to a straight vertical line;
around the solstices (June and December) the curve is at its most pronounced.
Does the shaded area ever cover more than half the world?
No — the terminator always splits the Earth into two equal halves, one in daylight and
one in night, regardless of season. What changes seasonally is how that 50/50 split is
distributed between hemispheres: in June the curve favors longer daylight in the
Northern Hemisphere and shorter daylight in the Southern Hemisphere, and the reverse in
December — the same mechanism behind seasonal changes in day length.
How is the sun's position calculated without a live astronomy API?
From two values computed from the current date and UTC time: the sun's declination
(how far north or south of the equator it sits directly overhead, cycling smoothly
between about +23.44° and -23.44° over the year — Earth's axial tilt) and the
subsolar longitude (which line of longitude currently has the sun at solar noon,
sweeping 15° every hour as the Earth rotates). Both are well-known astronomical
approximations accurate to roughly ±1°, recalculated live every 30 seconds.