How day length changes with latitude and season
From twelve hours all year on the equator to 22 hours in June at 65° north: day length by latitude, and how fast it changes.
The numbers
How long is the day on the equinox?
In 2026 the March equinox falls at about 14:46 UTC on 20 March and the September equinox at about 00:05 UTC on 23 September. On those days the day lasts longer than twelve hours everywhere in the table below.
| City | Latitude | Day on 20 Mar | Day on 23 Sep | Equal day and night, spring | Equal day and night, autumn |
|---|---|---|---|---|---|
| Edinburgh | 56.0° N | 12 h 11 min | 12 h 09 min | 17–18 Mar | 25–26 Sep |
| London | 51.5° N | 12 h 10 min | 12 h 09 min | 17–18 Mar | 25–26 Sep |
| New York | 40.7° N | 12 h 09 min | 12 h 07 min | 16–17 Mar | 25–26 Sep |
| Madrid | 40.4° N | 12 h 08 min | 12 h 07 min | 16–17 Mar | 25–26 Sep |
| Mumbai | 19.1° N | 12 h 07 min | 12 h 07 min | 13–14 Mar | 29–30 Sep |
| Singapore | 1.4° N | 12 h 06 min | 12 h 06 min | never | never |
| Sydney | 33.9° S | 12 h 09 min | 12 h 08 min | 24–25 Mar | 19–20 Sep |
| Cape Town | 33.9° S | 12 h 08 min | 12 h 09 min | 23–24 Mar | 18–19 Sep |
The date with equal day and night has a name of its own, the equilux. In the northern hemisphere it comes a few days before the March equinox and a few days after the September one, the more days the nearer you live to the equator; in the southern hemisphere it is the other way round.
Two reasons
Why the day wins
On the equinox the centre of the sun spends exactly half of its daily circle above the geometric horizon. Two things tip the balance towards the day:
- Sunrise and sunset are timed by the edge of the sun, not its centre. The sun’s radius is about 16 arcminutes, so the first and last glint come while the centre is still below the horizon.
- The atmosphere bends sunlight by about 34 arcminutes at the horizon, lifting the sun into view while it is geometrically below the horizon.
Together they make the sun count as risen while its centre is 0.83° below the horizon. On the equator the sun sinks vertically, 15° an hour, so 0.83° takes about 3.3 minutes at each end: the day is about six and a half minutes longer than the night. At 52° north the path is slanted, meeting the horizon at 38°, and the same 0.83° takes over five minutes at each end: the day wins by about eleven minutes.
A surprise
On the equator day and night are never equal
Away from the equator the length of the day changes through the year, so on some date it passes exactly twelve hours. On the equator the geometric day is twelve hours long every day of the year, and the edge of the sun and refraction add their six or seven minutes every day as well. In Singapore the day never drops below 12 hours 4 minutes. For the rest of the year’s pattern, see how day length changes with latitude.
Over a whole year
More daylight than darkness everywhere
Because the day wins at both ends every day, everywhere on Earth gets slightly more daylight than darkness over a year. Worked out for 2026: 4,422 hours on the equator, 50.5% of the year; 4,441 hours at 30° latitude; 4,482 hours at 52°, 51.2%; and 4,592 hours at 70°, 52.4%, where the sun lingers longest near the horizon. Add twilight, and the dark part of the year shrinks further.
The equinox itself is a moment, not a day: the instant the sun crosses the celestial equator. The winter solstice page lists the coming solstices and equinoxes to the minute.
Keep reading
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