How to use it
- Pick a city or enter latitude and longitude (decimal degrees; south and west negative). “Use my location” asks your browser for coordinates once.
- Choose the date and confirm the time zone – it is set from the city or your browser, with the UTC offset shown.
- Read sunrise and sunset, then solar noon, day length and the three twilight periods.
- Check the seven-day table to see how fast the days are getting longer or shorter.
- Copy the summary or the link to this location and date.
Example
London (51.5074° N, 0.1278° W) on 21 June 2026, BST (UTC+01:00): sunrise 04:43, sunset 21:21, solar noon 13:02, day length 16 h 38 min. Civil twilight 03:55–22:09, nautical 02:41–23:24; there is no astronomical twilight because the Sun never gets 18° below the horizon that night. The same place on 21 December: sunrise 08:04, sunset 15:53, 7 h 49 min of daylight.
The NOAA solar algorithm
The Sun’s position comes from the low-precision formulas of Meeus (Astronomical Algorithms, ch. 25) as used by the NOAA Global Monitoring Laboratory’s solar calculator: geometric mean longitude and anomaly, equation of centre, apparent longitude, obliquity of the ecliptic, hence the declination δ and the equation of time E. The hour angle of sunrise follows from the spherical-trigonometry relation below; the event time is computed twice, the second pass using the solar position at the time found by the first.
cos H = cos(90.833°) / (cos φ · cos δ) − tan φ · tan δ
sunrise (UTC minutes) = 720 − 4·(λ + H) − E; sunset = 720 − 4·(λ − H) − E
solar noon = 720 − 4·λ − E (φ latitude, λ east longitude, E equation of time in minutes)When |cos H| > 1 the Sun never reaches the horizon that day: the tool reports polar day or polar night, decided by the Sun’s altitude at noon. Twilight uses the same relation with 96°, 102° and 108° in place of 90.833°. Times are given in the chosen IANA time zone with the offset valid on that date (daylight-saving aware), and events are matched to the local civil date even for zones 12–14 hours from UTC.
Accuracy: the NOAA method is good to about one minute for latitudes below 72° and dates between 1900 and 2100; refraction varies with air temperature and pressure, so observed times can differ by a minute or two, more near the poles where the Sun crosses the horizon at a shallow angle. Elevation above sea level and local hills are not taken into account.
Sources: NOAA Global Monitoring Laboratory – Solar Calculator, NOAA – Solar calculation details, Meeus, Astronomical Algorithms (1998), ch. 25 – Solar coordinates, Twilight definitions (USNO).
Questions
- What time is sunrise and sunset today where I am?
- Click “Use my location” (your browser asks for permission; the coordinates are not stored or sent anywhere) or type your latitude and longitude. The time zone is taken from your browser so the times read like your clock.
- Why is solar noon not at 12:00?
- Clock time is the same across a whole zone, but the Sun is highest at a slightly different moment at every longitude (4 minutes per degree). The equation of time adds up to ±16 minutes more, and daylight-saving time shifts everything by an hour – in London on 21 June solar noon is at 13:02 BST.
- When is golden hour?
- Photographers’ golden hour is roughly the hour after sunrise and before sunset, when the Sun is below about 6° altitude. Civil twilight (the row in the results) is the “blue hour” on either side of it.
- Why does the table show no astronomical twilight in summer?
- North of about 48.5° latitude the Sun stays within 18° of the horizon all night around the June solstice, so the sky never becomes fully dark. Further north (above 54.5°) nautical twilight lasts all night, and above the Arctic Circle (66.5°) the Sun does not set at all.