Sunrise, Sunset, and Civil Twilight

NOAA solar-position algorithm: sunrise, sunset, civil / nautical / astronomical twilight, daylight minutes.

Run the calculator

Example

You enter

Latitude (deg) 40
Longitude (deg) -105
Date (YYYY-MM-DD) 2026-06-21
Timezone offset (hr) -6

You get

Declination 23.45 deg
Daylight 901 min
Sunrise 05:30
Sunset 20:31

Details, formula, and sources

NOAA Solar Position Algorithm (SPA) calculates declination, equation of time, sunrise / sunset / civil / nautical / astronomical twilight from latitude / longitude / date.

NOAA Solar Calculator (USNO algorithm) by name; Reda & Andreas, 'Solar Position Algorithm for Solar Radiation Applications' (NREL/TP-560-34302, 2008) by name.

Free at gml.noaa.gov/grad/solcalc.

Geometry is not forecasting. Avalanche advisory and incident commander govern.

Field names used by the API: lat_deg, lon_deg, date_iso, tz_offset_hours, declination_deg, daylight_minutes, sunrise, sunset

Atmospheric refraction −0.833° standard at horizonNOAA SPA