Daylight Calculator - Sunrise, Sunset and Day Length
Enter your latitude, longitude, date, and UTC offset to see today's sunrise and sunset times, total hours of daylight, solar noon, and all three twilight zones. The calculator uses the standard astronomical algorithm from Jean Meeus and accounts for atmospheric refraction. Results update as you type.
How the daylight calculator works
This calculator uses the algorithm from Jean Meeus's "Astronomical Algorithms" (2nd edition), the same source used by the NOAA Solar Calculator. It determines the Julian Day Number for your date, then computes solar declination (the sun's angle above or below the celestial equator) and the Equation of Time (a small correction for Earth's elliptical orbit). From those values it derives the solar hour angle, which is half the angular distance the sun travels from sunrise to sunset. Sunrise and sunset are defined as when the sun's upper limb touches the horizon, corrected for atmospheric refraction (the standard 0.833 degree adjustment). Results should match official almanac values within one to two minutes for most mid-latitude locations.
What the twilight zones mean
Beyond civil sunrise and sunset, three twilight zones are recognized by astronomers and navigators. Civil twilight begins when the sun is 6 degrees below the horizon: there is generally enough natural light for most outdoor activities without artificial light. Nautical twilight begins at 12 degrees below the horizon; at sea, the horizon is still visible for celestial navigation. Astronomical twilight begins at 18 degrees below the horizon, at which point the sky is dark enough that all but the faintest stars are visible to the naked eye. Full astronomical darkness only truly arrives once the sun has passed 18 degrees below the horizon.
Why day length changes with latitude and season
Earth's axis is tilted 23.45 degrees relative to its orbital plane. As Earth orbits the Sun, this tilt causes the Northern Hemisphere to face the sun more directly in June (summer) and less directly in December (winter), reversing for the Southern Hemisphere. At the equator, day length barely changes across the year because it is roughly equidistant from both poles. At higher latitudes the effect amplifies: above the Arctic Circle (66.5 degrees N) the sun does not rise at all on the winter solstice and does not set on the summer solstice. The equinoxes in March and September are the days when every location on Earth receives nearly 12 hours of daylight.
Solar noon and the Equation of Time
Solar noon is not always at 12:00 on your clock. It shifts for two reasons: your longitude within your time zone, and the Equation of Time. The Equation of Time is a correction of up to about 16 minutes caused by Earth's elliptical orbit (Earth moves faster when close to the Sun in January) and the tilt of its axis. The two effects combine to produce the analemma, the figure-8 shape traced by the sun's position at noon throughout the year. This calculator accounts for both corrections to give you an accurate solar noon in local clock time.
Approximate day length by latitude at solstices and equinoxes
| Latitude | Summer solstice | Equinox | Winter solstice |
|---|---|---|---|
| 0° (Equator) | 12 h 7 min | 12 h 7 min | 12 h 7 min |
| 10° | 12 h 43 min | 12 h 7 min | 11 h 31 min |
| 20° | 13 h 21 min | 12 h 8 min | 10 h 55 min |
| 30° | 14 h 5 min | 12 h 8 min | 10 h 11 min |
| 40° | 14 h 58 min | 12 h 8 min | 9 h 18 min |
| 50° | 16 h 18 min | 12 h 9 min | 7 h 50 min |
| 60° | 18 h 52 min | 12 h 11 min | 5 h 28 min |
| 66.5° (Arctic Circle) | 24 h | 12 h 11 min | 0 h (polar night) |
| 70° | 24 h (>2 mo) | 12 h 12 min | 0 h (polar night) |
| 90° (North Pole) | 24 h (6 mo) | 12 h 15 min | 0 h (6 mo) |
Day length varies significantly with latitude. These values are approximate for mid-latitude sites and use standard atmospheric refraction.
Frequently asked questions
Why does the calculator show a different sunrise than my weather app?
Small differences of one to three minutes are normal and arise from how each tool handles atmospheric refraction, the precision of the algorithm, and whether it applies a correction for the observer's altitude above sea level. This calculator assumes sea-level observation and uses the standard 0.833-degree refraction adjustment. Weather apps may also apply local terrain corrections.
What is the Equation of Time?
The Equation of Time is a correction, up to about 16 minutes, applied to solar noon because Earth travels faster in its orbit when close to the Sun (around early January) and slower when farther away (around early July). The tilt of Earth's axis adds another oscillation. The combined effect means that "clock noon" and "sun noon" only match on four days per year, around April 15, June 13, September 1, and December 25.
Why does the calculator show "None (polar)" for some twilight times?
At very high latitudes near the poles, the sun may not descend far enough below the horizon to reach some twilight thresholds, especially in summer. For example, in Reykjavik (64 degrees N) around the summer solstice, the sun never drops to the 18-degree astronomical twilight threshold. You will see "None (polar)" whenever a twilight zone is not reached for the date and location you entered.
How do I account for daylight saving time?
Select the UTC offset that is already in effect for your location on the date you entered. For example, New York uses UTC-5 (EST) in winter and UTC-4 (EDT) in summer. If you select UTC-5 but daylight saving is active, your displayed times will be one hour behind. Simply pick the offset that matches your clock time on that date.
What is solar declination and why does it matter?
Solar declination is the angle between the sun and the celestial equator, ranging from +23.45 degrees at the June solstice to -23.45 degrees at the December solstice. It is zero at the equinoxes. Declination determines how high the sun rises in the sky and, combined with your latitude, controls exactly how many hours of daylight you receive on any given day.
Can I use this calculator for any location on Earth?
Yes, for latitudes between about -65 and +65 degrees the results are highly accurate. Between 65 and 90 degrees, polar effects such as midnight sun and polar night occur, and the calculator correctly identifies those conditions. For latitudes above 80 degrees or below -80 degrees, small edge-case differences may appear near the transitions into and out of polar day or night.