Science & history · Seasons and clocks
Day length changes fastest near the equinoxes
Around the solstices one day's daylight is almost the same as the next. Around the equinoxes it changes quickly.
Your daylight, day by day
Worked out in your browser for your place. Choose a place on the Sun's Today page.
Why
The Sun's north–south rate changes through the year: it is greatest as the Sun crosses the celestial equator, near the equinoxes, and close to zero at the solstices. The length of daylight follows it. How big the daily change is depends on latitude: near the equator it is small all year, and far from it the swings are large. The page shows yours, calculated with USNO's sunrise and sunset definitions.
Clock changes are not daylight changes
A day with a daylight-saving change is 23 or 25 hours long on the clock, but the Sun does not care: the page compares the actual elapsed daylight, and shows the clock shift separately.
Sources
- US Naval Observatory The Equation of Time (opens in a new tab) for apparent vs mean solar time, its two causes, the analemma · checked 2 October 2026
- US Naval Observatory Rise, Set, and Twilight Definitions (opens in a new tab) for sunrise/sunset and the three twilights; refraction and accuracy caveats · checked 2 October 2026
- Cool Moon Facts How the Sun pages calculate for the engine, its definitions, its independent checks and its limits