Sunrise, sunset, noon and the twilights are just the moments the sun’s height crosses a line: 0°, 6° below, 12° below, and its highest point. Plot the height against the clock and every event of the day is on one curve.
Civil twilight runs until the sun is 6° below the horizon (enough to read outside), nautical to 12° (the horizon fades) and astronomical to 18° (the sky is fully dark). Near the poles in summer the sun never gets that low.
Solar noon, when the sun is highest, moves by your longitude within the zone, by the equation of time (up to 16 minutes either way through the year) and by daylight saving. Few places ever have it on the stroke of twelve.
On the equator the day is about 12 hours all year. In London it runs from 7h 50m to 16h 39m; in Reykjavik from 4h 07m to 21h 10m; and within the Arctic Circle it runs from nothing at all to 24 hours.
Sunrise is when the sun’s upper edge meets the horizon, and the disc is about half a degree across, so the centre is still 16 arcminutes below. Refraction lifts the image by about 34 arcminutes more, so when you watch the sun touch the horizon it is already geometrically below it. Together that puts the event at 90.833° from the vertical rather than 90°, the constant this tool uses.
It is the one fact everybody remembers about the equinox, and it is wrong everywhere on Earth, always in the same direction. On the March equinox the day runs to 12h 07m at the equator and 12h 08m in London. Never 12h 00m, anywhere. The day when light and dark really are equal is the equilux: in London a couple of days before the March equinox, and again in late September. Singapore never has one at all, because every day of its year is longer than 12 hours.
Add London’s longest and shortest days together: 16h 39m plus 7h 50m is 24h 28m, not 24 hours. The refraction bonus is paid on both days, so you count it twice.
The Earth’s axis is tilted and its orbit is an ellipse, so the sun is sometimes ahead of an even clock and sometimes behind it: about 14 minutes behind around Feb 13 and 16 minutes ahead around Nov 1. The tilt gives the slow twice-a-year swing and the elliptical orbit the once-a-year one. Add your longitude within your time zone (4 minutes for every degree) and any daylight saving, and that is why solar noon so rarely lands on 12:00.
In London the earliest sunset, 15:51, is on Dec 13, but the shortest day is Dec 22, 9 days later. The same equation of time that moves solar noon makes the evenings start to draw out before midwinter while the mornings keep getting darker. Look at the sunrise and sunset curves in the year chart: they are not mirror images.
The golden hour is the time the sun spends between the horizon and 6° up. The name only fits the mid-latitudes where it was coined: on 3 September it lasts about 28 minutes in Singapore, where the sun climbs almost vertically, and about 45 minutes in London. This tool prints the real duration for your place and day.
The sun rises due east only at the equinoxes (nearly: 89° in London, because of refraction). In London at midsummer it rises in the north-east, at 49°, and at midwinter in the south-east, at 128°. The path chart shows it: the high summer track is long and tall, the winter track short and low. At solar noon the sun is 61.9° up in June and 15.1° in December, so a 1 m post casts a shadow of 0.53 m at midsummer noon and 3.7 m at midwinter noon.
Land and sea take weeks to warm up. Peak daylight is the solstice, but peak temperature lags by a month or two: the same reason the hottest part of the day is after noon, not at it.
Each is one hour of the day at your chosen reference latitude, 24 in total, drawn only if the sun is genuinely above the horizon at that hour. In deep summer at a high latitude all 24 are lit at once, which is exactly what “24 hours of daylight” means: a count, not a metaphor. Trømso is there as a real, inhabited place at 69.6°N that gets true 24-hour daylight around the June solstice and 24-hour night around December.
The times use the NOAA approximation, good to within about two minutes at mid-latitudes (about one near the equator) and less near the poles, where the sun meets the horizon at a shallow angle and a small error in height becomes a large one in time. The horizon is flat and at sea level, with standard refraction; hills and buildings change what you see by minutes. The height and bearing through the day use that day’s declination, so they are exact at the events and about a tenth of a degree out between them. Continent outlines on the globes are simplified.
The period when the sun is just below the horizon, up to 6° down: dim but still light enough to see outside without artificial lighting. It is why it is bright well before sunrise and after sunset. Nautical twilight runs to 12° below and astronomical twilight to 18°, when the sky is fully dark.
Three things move it. Your longitude within your time zone shifts it by 4 minutes for every degree away from the zone’s central meridian; the equation of time, from the Earth’s tilt and elliptical orbit, moves it by up to about 16 minutes either way through the year; and daylight saving moves the clocks an hour while the sun does not.
Because of the equation of time. Solar noon is moving later through December, so sunset keeps drifting later after its earliest point even while the day is still getting shorter. In London the earliest sunset is 9 days before the shortest day, and the latest sunrise comes after it.
Because land and sea take weeks to warm up. Peak daylight is the solstice, but peak temperature lags by a month or two, the same reason the hottest part of the day is after noon, not at it.
Within about two minutes at mid-latitudes, and about one near the equator, for a flat sea-level horizon. Mountains, tall buildings and altitude can shift the real moment you see the sun by several minutes either way, and close to the Arctic and Antarctic circles the sun meets the horizon so shallowly that the times are only indicative.
The time when the sun is between the horizon and 6° above it, when light is low and warm. It is an angle, not an hour: near the equator it is nearer half an hour, and in high-latitude summer the sun can sit inside the band for most of a day.
Due east and sets due west only at the equinoxes. In summer it rises and sets towards the north (in the northern hemisphere), in winter towards the south, and the further from the equator the bigger the swing. The sky chart shows the track for the chosen day against the solstices.
Daylight saving. The clocks move an hour but the sun does not, so sunrise and sunset take a vertical step on the changeover dates. Phoenix, which keeps no daylight saving, has a smooth curve: compare it with Los Angeles to see what the step is.
Each one is a single hour of the day at your chosen reference latitude, 24 in total. A ray is only drawn if the sun is genuinely above the horizon at that hour; in deep summer at a high latitude all 24 are lit at once.
This page has changed in 6 archived releases, but each of those was a site-wide pass, so none is attributable to this tool on its own and none is listed here. That is not a claim that the tool never changed — a release that reworked many pages at once may well have altered this one too. The changelog has them.