Day Night Map — Live World Terminator and Subsolar Point
Live world map showing where it is day and where it is night right now. The yellow line is the terminator — the boundary between the lit and unlit hemispheres. The yellow sun marker is the subsolar point, the single spot on Earth where the sun is directly overhead at this moment. Click anywhere for that location's local sunrise, sunset, and current sun phase.
What is the day/night terminator? Definition and Geographic Facts
The terminator (sometimes called the grey line or twilight line) is the moving boundary between the lit and unlit hemispheres of Earth. It is a great circle — the largest possible circle drawn on a sphere — exactly 90° away from the subsolar point, the single spot where the sun is directly overhead. Because Earth rotates once every 24 hours, the terminator sweeps westward across the planet at 15° of longitude per hour — about 1,670 km/h at the equator.
Day/night terminator definition (short): the great circle on Earth where the sun is exactly on the horizon — the dividing line between day and night. Subsolar point:the single point on Earth where the sun is at the zenith (directly overhead). It sits at latitude equal to the sun's current declination, ranging from 23.44°N at the June solstice to 23.44°S at the December solstice. Day/night ratio: Earth is always lit on exactly half its surface (ignoring atmospheric refraction, which adds a small ~0.5% bias). The other half is in night.
Where is it night right now? Everywhere on the shaded side of the live map above. The night region is the hemisphere centred on the antisolar point— the longitude exactly 180° from the subsolar point. Conversely, day is everywhere on the unshaded side. Because the terminator is always moving, “night right now” is a snapshot — wait 30 seconds and the terminator has shifted 0.125° westward; wait an hour and it has moved 15° (about a US time zone).
How to use this Day/Night Map
- Open the world map. The yellow line is the terminator — the boundary between day and night right now. The shaded region is the night side (everywhere the sun is below the horizon). The yellow sun marker shows the subsolar point: the single spot on Earth where the sun is directly overhead at this exact moment.
- Watch the terminator move. The map updates every 30 seconds. The terminator drifts westward at 15° of longitude per hour — about 0.125° per tick. Over a full 24 hours it traces a complete sine wave that meets itself at the same spot tomorrow, slightly offset by the seasonal change in solar declination.
- Click anywhere for local sunrise, sunset, and sun phase. Click any point on the map to open a popup with that location's approximate local time, today's sunrise and sunset, current sun phase (day, twilight, night), and the sun's altitude in degrees above or below the horizon. Useful for planning calls, photography, and astronomy.
- Read the seasons explainer below. The terminator is a great circle 90° from the subsolar point. As Earth's axial tilt rocks the subsolar point between 23.4°N (June solstice, Tropic of Cancer) and 23.4°S (December solstice, Tropic of Capricorn), the terminator's slant changes — that's why the day-night line is curved on a flat map and why polar day and polar night happen.
Where is the sun right now? Sample cities
Click each city on the live map above to see its current sun phase, today's sunrise and sunset, and approximate local time. The map updates every 30 seconds — by the time you click, the terminator may have moved a few hundred metres.
How the terminator moves: 15° per hour, westward
The day/night line moves continuously, never stopping. Its speed is exactly Earth's rotation rate: 15° of longitude per hour, or about 0.25° per minute. At the equator, that translates to a ground speed of 1,670 km/h (1,038 mph) — faster than a commercial jet. At the Arctic Circle the linear speed slows to about 680 km/h; at the poles it spirals to zero (and the terminator can stay put for months).
Three observations follow from this constant 15°/hour motion:
- You can outrun the terminator. Concorde at 2,180 km/h could fly westward over the Atlantic and watch the sun rise in the west— its ground speed exceeded the terminator's eastern speed at temperate latitudes. The SR-71 Blackbird (3,500 km/h) could do this anywhere.
- Solar noon happens at every longitude exactly once a day.The subsolar point's longitude advances 15° westward per hour, completing a full 360° loop every 24 hours.
- The terminator's slant changes throughout the year. At the equinoxes (March 21, September 23), the terminator runs north-south through the poles; the day/night line is vertical on the map. At the solstices, the terminator tilts by 23.4° relative to the meridians, leaving the polar regions either fully lit (midnight sun) or fully dark (polar night).
Twilight zones: civil, nautical, astronomical
After sunset and before sunrise, the sun is below the horizon but still illuminates the upper atmosphere. Astronomers and navigators distinguish three official twilight phases based on the sun's angular depth below the horizon:
- Civil twilight(0° to 6° below horizon): bright enough for outdoor activity without artificial light. The brightest stars and planets are visible. The “blue hour” falls in this phase — popular for cityscape photography.
- Nautical twilight (6° to 12° below): the horizon is still visible against the sky and brighter stars are out. Historically used for celestial navigation by sextant — both horizon and stars are simultaneously visible.
- Astronomical twilight(12° to 18° below): the sky is dark enough for most astronomy but residual sky glow is still detectable. End of evening astronomical twilight = the start of “true night.”
Each twilight band is a circular zone parallel to the terminator at the appropriate angular distance from the subsolar point. On the live map above, the click popup identifies which twilight phase any clicked point is currently in.
The subsolar point and the seasons
The subsolar pointis the spot on Earth where the sun is at the zenith — directly overhead — at any given moment. Its latitude equals the sun's solar declination, which depends on Earth's axial tilt and orbital position. Over the course of a year, the subsolar latitude oscillates between two bounds:
- +23.44°N (June solstice, around 21 June): the subsolar point is on the Tropic of Cancer. The Northern Hemisphere has its longest day of the year; the Arctic Circle sees the midnight sun.
- 0° (equinoxes, around 21 March and 23 September): the subsolar point is on the Equator. Day and night are almost exactly 12 hours everywhere; the terminator is vertical on a map.
- -23.44°S (December solstice, around 21 December): the subsolar point is on the Tropic of Capricorn. The Southern Hemisphere has its longest day; the Antarctic Circle sees the austral midnight sun.
The two tropics, the two polar circles, and the equator together define the major seasonal geometry of Earth's solar geometry. The subsolar point's annual path traces a figure-eight (the analemma) when plotted at the same clock time each day, because of the equation of time — the difference between mean solar time and apparent solar time caused by Earth's elliptical orbit and axial tilt.
Why the day/night line is curved on a flat map
On a globe, the terminator is a perfect great circle — straight relative to the sphere, just like the equator. On a flat map (Mercator, Robinson, Mollweide, whichever), the projection process distorts straight lines on the sphere into curves on the page. The flatter the map, the more the curve.
The amount of curvature depends on the season:
- At the equinoxes, the subsolar point is on the equator. The terminator runs straight north-south through both poles, so it appears as two vertical meridians on a Mercator map (90° east and west of the subsolar longitude). No visible curvature.
- At the solstices, the subsolar point is at one of the tropics. The terminator tilts 23.4° relative to the meridians and traces an S-shaped sine wave across a flat map. The curve is most pronounced near the polar regions, where the terminator can leave one pole entirely in light and the other entirely in dark.
- Throughout the year, the curve's amplitude varies smoothly between zero (equinox) and 23.4° (solstice). On the live globe-projection map above, the curve is the genuine spherical great circle — no flat-map distortion.
Related tools and resources
For the major lines of latitude that shape the day/night terminator's annual motion, see the Equator, Tropic of Cancer, Tropic of Capricorn, Arctic Circle, and Antarctic Circle tools. The Prime Meridian tool covers the longitude reference that anchors the time-zone system.
For point-specific solar data, use the Sun Position Calculator (azimuth, elevation, and shadow direction at any time and place), the Sunrise & Sunset Calculator (precise rise/set/twilight times anywhere worldwide), or the Time Zone Finder for the political time zone at any location. To compare two locations live, the Time Difference Calculator shows working-hours overlap between any 2-5 cities.
Frequently asked questions about the day/night map
What is a day/night map?
A day/night map is a world map showing the boundary between day and night at the current moment. The day side is where the sun is above the horizon; the night side is where it is below. The boundary curve between them is called the terminator. Day-night maps update in real time because Earth rotates 15° per hour, moving the terminator continuously around the planet.
What is the terminator?
The terminator is the dividing line between the lit and unlit hemispheres of Earth. It is a great circle exactly 90° from the subsolar point (the spot where the sun is directly overhead). As Earth rotates, the terminator sweeps westward at 15° of longitude per hour. The terminator is curved when projected on a flat map because Earth's axial tilt of 23.4° offsets the subsolar point from the equator most of the year.
What is the subsolar point?
The subsolar point is the single point on Earth where the sun is directly overhead — at the local zenith — at any given moment. Its latitude equals the sun's current declination (between 23.4°N at the June solstice and 23.4°S at the December solstice); its longitude moves westward at 15° per hour, completing a full circle every solar day. The subsolar point traces a path between the Tropic of Cancer and the Tropic of Capricorn over the course of a year.
Where is it night right now?
Night right now is everywhere the sun is below the horizon. On the live map above, the night region is the shaded area on the unlit hemisphere. Roughly speaking: it is night in the half of the world centred on the antisolar point (the longitude exactly 180° from the subsolar point). The map updates every 30 seconds so you can watch the terminator move.
Where is it day right now?
Day is the unshaded region of the live map — everywhere the sun is currently above the horizon. The brightest sun (highest in the sky) is at the subsolar point, marked on the map by the yellow sun icon. Sunrise is happening along the eastern edge of the terminator; sunset along the western edge.
Why is the day/night line curved on a flat map?
Because Earth is tilted on its axis by 23.4° relative to its orbital plane. The terminator is a great circle on the spherical Earth, but when projected on a flat (Mercator or similar) map it appears as an S-shaped curve because the projection distorts great circles into wavy lines. On a globe, the terminator is straight — exactly 90° from the subsolar point. The amount of curvature you see on the flat map depends on the time of year: it is straightest at the equinoxes and most curved at the solstices.
How fast does the terminator move?
The terminator moves at 15° of longitude per hour — Earth's rotation rate. At the equator, that corresponds to about 1,670 km/h on the ground. At higher latitudes it slows in absolute terms (cos(lat) × 1,670 km/h) but stays at 15° per hour in longitude. Over 24 hours the terminator completes a full circuit and ends up at almost the same position, offset slightly by seasonal change in solar declination.
Why are the days different lengths in summer and winter?
Because Earth's axial tilt of 23.4° causes the terminator to slant relative to the equator. In June (Northern Hemisphere summer), the subsolar point is in the Northern Hemisphere, so the terminator slants such that more of the Northern Hemisphere is in daylight at any given time — longer days in the north, shorter in the south. In December, the situation reverses. At the equator, days are always within a few minutes of 12 hours regardless of season.
What are civil, nautical, and astronomical twilight?
After sunset (and before sunrise), the sun is below the horizon but still illuminates the upper atmosphere. The three official twilight phases are: civil twilight (sun 0° to 6° below horizon — bright enough for outdoor activity without artificial light); nautical twilight (sun 6° to 12° below — horizon still visible, brightest stars out); and astronomical twilight (sun 12° to 18° below — sky truly dark for deep-sky astronomy at the lower end). Each phase corresponds to a band on the day/night map running parallel to the terminator at the appropriate angular distance from the subsolar point.
Why doesn't the polar region see normal day/night?
Because the terminator runs through the polar regions during summer and winter solstices. At the June solstice, the entire region north of the Arctic Circle (66.5°N) is in continuous daylight — the terminator does not reach it — and the entire region south of the Antarctic Circle (66.5°S) is in continuous darkness. Six months later in December, the situation is reversed. This phenomenon is called the midnight sun in summer and polar night in winter.
How accurate is this day/night map?
The terminator is computed from the current UTC time using NOAA's solar declination and equation-of-time formulas — accurate to within about 30 seconds of the true position. Sunrise and sunset times in the click popup come from SunCalc (atmospheric refraction included, accurate to about 1 minute at typical latitudes; less accurate inside the polar regions during midnight sun / polar night). Approximate local time at any clicked point uses the longitude/15 hours rule and does not account for political time zones or daylight saving.
How is this different from a time-zone map?
A time-zone map shows political zones — chunks of time set by countries for civil convenience. The day/night terminator is astronomical — it follows the actual position of the sun and ignores political boundaries. China, for example, uses a single time zone (UTC+8) across its entire 60° width of longitude, but the day/night line moves through the country normally. France and Spain use Central European Time even though much of their land is west of the Greenwich meridian. The day/night map shows what the sun is actually doing; a time-zone map shows what governments have agreed to call it.
Data sources and methodology
The subsolar point is computed from the current UTC time using NOAA's solar declination formula and the equation of time (accurate to within ~30 seconds at any time of year). The terminator is the great circle 90° from the subsolar point, rendered as a 361-point polyline using lat = atan(-cos(dLng) / tan(lat_s)). Sunrise and sunset times in the click popup come from the SunCalc npm package (atmospheric-refraction-aware). Approximate local time uses the longitude/15 hours rule and does not account for political time zones or daylight saving — for legal local time, use the Time Zone Finder. The basemap is OpenFreeMap Liberty rendered on a globe by MapLibre GL JS. The map updates every 30 seconds; refreshing more often would not show meaningfully more motion.