Find hours of daylight for any location and date, with day-over-day change and solstice comparisons.
About this calculator
Day length is the period between sunrise and sunset, calculated using the standard NOAA solar position algorithm with atmospheric refraction correction (zenith 90.833°).
Times shown are in local solar time for the given longitude, not civil clock time.
Day length
Hours of daylight on 2026-03-21 at latitude 51.51°.
Solstice comparison
Solar calculations based on NOAA algorithms. Times are local solar time, not civil clock time.
Also in Calendar Reference
Dates & Time
Find the hours of daylight for any location and date, with day-over-day change and comparisons to the summer and winter solstices.
Day length is calculated from the sun's hour angle at sunrise and sunset using NOAA solar algorithms. The calculator also computes the day length for the previous day to show whether daylight is increasing or decreasing, and compares against the shortest and longest days of the year.
Near the equator, day length stays close to 12 hours year-round. At higher latitudes, the difference between summer and winter can be dramatic — London sees about 16 hours 38 minutes at the summer solstice but only 7 hours 49 minutes at the winter solstice.
Frequently asked questions
The rate of change in solar declination is greatest near the equinoxes, causing day length to shift by several minutes per day. Near the solstices, the change slows to almost zero.
No — the seasons are reversed. When the northern hemisphere has its longest day (June solstice), the southern hemisphere has its shortest, and vice versa.
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