Day Length Calculator
Approximate day length (hours of sunlight) based on latitude and day of year.
Formula
Daylight ≈ 12 ± 7.6·sin((n-81)·2π/365)
Summer solstice at 40°N
Inputs
- Day of Year (1-366): 172
- Latitude (degrees, -90 to 90): 40
~14.5 hours daylight
Frequently asked questions
Is this accurate?
Approximate formula; actual values depend on altitude, atmospheric refraction