Calculateur de Durée du Jour
Calculez la durée d'ensoleillement pour une date et un lieu donnés.
Daylight Hours
14.92 hrs
Daylight Hours vs Latitude
Formule
## Daylight Duration The number of hours between sunrise and sunset depends on latitude and the Sun's declination (which changes through the year). ### Formula **D = (2/15) × arccos(-tan(φ) × tan(δ))** hours where φ = latitude and δ = solar declination (both in degrees, converted to radians for calculation). Solar declination ranges from -23.44° (Dec solstice) to +23.44° (Jun solstice).
Exemple Résolu
New York (40.7°N) at summer solstice (declination = 23.44°).
- 01cos(H) = -tan(40.7°) × tan(23.44°)
- 02= -0.860 × 0.433 = -0.3726
- 03H = arccos(-0.3726) = 111.86°
- 04D = 2 × 111.86 / 15 = 14.91 hours of daylight
Questions Fréquentes
What declination should I use?
Solar declination varies from +23.44° (June solstice) to -23.44° (December solstice). At equinoxes it is 0°, giving exactly 12 hours everywhere.
What happens at the Arctic Circle?
At 66.56° latitude, the formula gives 24 hours at summer solstice (midnight sun) and 0 hours at winter solstice (polar night).
Does this include twilight?
No. This gives centre-of-disc sunrise to sunset. Civil twilight adds roughly 30-40 minutes of usable light at each end.