Daylight Change Per Day Calculator
See how many minutes of daylight you gain or lose each day at any city or latitude — today’s change in minutes and seconds, how much sunrise and sunset move, the weekly and monthly change, the next solstice turning point, the fastest-changing days of the year and a day-by-day table — from the NOAA solar equations, or from two day lengths you measured.
How it works
change per day = day length on the date − day length the day before · day length = sunset − sunrise, with cos H = cos 90.833° ÷ (cos φ · cos δ) − tan φ · tan δ and day length ≈ 8·H minutes (H in degrees) · δ = solar declination from the NOAA solar equations · from your own readings: (day length now − day length earlier) × 60 ÷ days between them
Day length depends on your latitude and on the Sun’s declination — how far north or south of the equator the Sun sits, which swings between +23.44° in June and −23.44° in December. The declination changes fastest at the March and September equinoxes and stalls at the solstices, so day length changes fastest in spring and autumn (two to three minutes a day at mid-latitudes, far more near the Arctic Circle) and hardly at all in midsummer and midwinter. Pick a city or enter a latitude and the calculator uses the NOAA solar equations to find sunrise and sunset for your date and the day before, and gives the difference in minutes and seconds — the same “difference” column timeanddate prints. It also shows how much of that change comes in the morning and how much in the evening, the change over the next week and month, when the next solstice turns the trend around and how much daylight is still to come or go before then, the fastest-changing days of the year, and a day-by-day table and chart. If you already have two day lengths from a sunrise table, switch to “Two day lengths I have” and it averages the change over the gap between them.
Worked example
In New York on October 19, 2026 the day lasts 10 h 58 min 01 s, which is 2 min 34 s shorter than on October 18: sunrise comes 1 min 06 s later and sunset 1 min 28 s earlier. Over the next week the day loses 18 minutes, and over the next 30 days 1 h 09 min. The shortest day is December 21, 2026 at 9 h 15 min, so another 1 h 43 min of daylight will go before the trend turns. The fastest change of the year at this latitude is about 2 min 43 s a day, around March 19 and September 25. With your own readings instead — 12.70 hours a week ago and 12.00 hours today — the day lost 42 minutes in 7 days, 6.00 minutes a day.
Sources: NOAA — Solar Calculation Details · NOAA Solar Calculator · US Naval Observatory — Rise, Set and Twilight Definitions
Frequently asked questions
How many minutes of daylight do we gain each day?
It depends on the date and your latitude. At about 40° N (New York, Madrid, Beijing) the day grows by roughly 2 min 40 s a day around the March equinox and shrinks by about the same amount around the September equinox, but changes by only a few seconds a day near the solstices. Near the equator the change is a few seconds a day; in Oslo or Anchorage it tops 5 minutes.
When do the days start getting longer?
In the Northern Hemisphere, right after the December solstice (December 21 or 22). At first the gain is only a few seconds a day; it builds to its maximum around the March equinox. South of the equator the days start getting longer after the June solstice.
Why does sunset get later before the shortest day?
Because solar noon is drifting later by about 30 seconds a day in December. The day is still shortening, but the whole day is shifting later, so the earliest sunset comes in early December and the latest sunrise in early January.
Does daylight change at the same rate everywhere?
No. The farther you are from the equator, the faster day length swings. The rate is the same at all longitudes along one latitude, which is why only the latitude really matters here; the city or time zone only sets the clock times.
Can I use my own sunrise and sunset readings?
Yes. Choose “Two day lengths I have”, enter both day lengths in decimal hours (12 h 42 min = 12.70) and the number of days between them, and the calculator gives the average change per day, per week and per 30 days.
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This calculator is for educational purposes. Double-check important results before acting on them.