The edge of the dark, followed for 24 hours
The line between day and night crosses every place on Earth once a day. Along the equator it moves at 1,670 kilometres an hour. Follow it westward for 24 hours and watch the lights come on behind it.
The date line · sunset 06:11 UTC
Half of the Earth is always in daylight and half in night. The planet turns eastward under that division, so the edge of the night moves west across the ground, all day, every day.
This is the evening edge on 20 March, when day and night are equal and the line runs almost straight from pole to pole. It starts here, in the empty Pacific at the date line. Along the equator it covers 1,670 kilometres every hour.
Tokyo · sunset 08:53 UTC
Japan comes first. Its lights follow the coasts, because most of the inside of the country is mountain.
The lights on this map are real. They were recorded from orbit on cloud-free nights during 2016 and are shown coming on as the Sun sinks six degrees below the horizon, roughly when street lighting does.
Seoul · sunset 09:44 UTC
Fifty minutes later the line reaches the Korean peninsula. The south is bright from coast to coast.
The north is almost completely dark. From orbit it looks like a stretch of sea between South Korea and China, and its capital, Pyongyang, gives off about as much light as a small South Korean town.
Singapore · sunset 11:16 UTC
Night does not fall at once. Between sunset and the point where the Sun is six degrees under the horizon there is still enough light to see by. At the equator the Sun goes straight down and that takes 24 minutes.
Farther from the equator the Sun sets at a slant. At 60 degrees north, on this date, the same six degrees take 48 minutes.
Delhi · sunset 13:02 UTC
The north of the Indian subcontinent lights up as a single field, from Lahore across Delhi to Kolkata. It follows the plains of the Indus and the Ganges, among the most densely settled land on Earth.
To the north the Himalaya and Tibet stay dark.
Cairo · sunset 16:06 UTC
Egypt at night is one thin line and a fan. Almost the whole population lives along the Nile and in its delta, on a small percentage of the country’s land. The desert on both sides is black.
Bucharest · sunset 16:28 UTC
Twenty minutes after Cairo the line reaches Bucharest, and under two hours later London. Europe is lit almost everywhere.
The line slows as it goes north, because the circles of latitude get shorter. At 45 degrees it covers about 1,180 kilometres an hour. North of about 57 degrees it drops below 900, and an airliner flying west could keep up with the sunset.
Mid-Atlantic · sunset 20:51 UTC
After Lisbon there is nothing to light. The line takes more than four hours to cross from Portugal to New York.
New York · sunset 23:08 UTC
São Paulo and Rio come on first, then the Caribbean, then the east coast of North America, lit without a break from Boston to Washington.
The eastern half of the United States is a dense net of towns and roads. Farther west the lights thin out.
Los Angeles · sunset 02:05 UTC
Mexico City, then Los Angeles three hours after New York. The coast of California is the last continuous band of light before the open ocean.
Mid-Pacific · sunset 04:11 UTC
From Los Angeles westward to Tokyo the line travels for nearly seven hours. Honolulu is the one bright point on the way.
The date line · sunset 06:11 UTC
Twenty-four hours after it started, the line is back where it began. It has crossed every place on Earth once and switched on everything people have built that shines.
It is already on its way to Japan again.
This is the Earth at this moment, worked out from your device’s clock. Somewhere along the line the Sun is setting, and on the far side of the night it is coming up.
The position of the Sun and every sunset time on this page are calculated, for 20 and 21 March 2026, with the low-precision formulas of the Astronomical Almanac. Sunset means the moment the Sun’s centre is 0.833 degrees below a flat horizon, the usual convention. The speeds are the Earth’s circumference at each latitude divided by 24 hours. The daylight side is NASA’s Blue Marble; the night side is NASA’s Black Marble, a composite of cloud-free nights in 2016, so the lights are those of 2016 and of the middle of the night, not of dusk on this date. There are no clouds, and the last view uses the same pictures for the present moment.