Sunlight Duration Calculator

Direct answer

Subtract the entered local sunrise clock time from the entered local sunset clock time. The U.S. Naval Observatory describes daylight duration as the time when any part of the Sun is above the horizon, typically the elapsed time from sunrise to sunset at low and mid latitudes. This calculator only performs that elapsed-time arithmetic on the times you supply.

Variables and formula

• Sunrise: local 24-hour clock time for sunrise.
• Sunset: local 24-hour clock time for sunset on the same date.

Daylight minutes = sunset clock minutes − sunrise clock minutes

Reproducible example

From 06:15 to 19:45, the daylight duration is 810 minutes, or 13.5 hours. The remaining part of a 24-hour day is 10.5 hours.

Interpretation

This result describes the stated clock-time span, not the amount of direct sun received by a garden bed, roof or window. Buildings, terrain, clouds and shade can reduce direct exposure even while daylight continues.

Assumptions and limitations

• Both times use the same local date and time zone.
• Sunset is not earlier than sunrise.
• The calculator does not predict astronomy, weather, plant needs or growing results.

Common mistakes

• Mixing clock times from different dates or locations.
• Treating daylight duration as hours of unshaded direct sunlight.
• Entering a sunset earlier than sunrise instead of checking the date or time zone.

Assumptions

• Both clock times use the same local civil date and time zone.
• Sunset is not earlier than sunrise.
• This calculator measures entered times only; it does not predict sunrise, sunset, weather, shade, plant exposure or growing outcomes.

Sources and methodology

CalcMotive publishes the formula and assumptions so you can decide whether the estimate fits your use case. See our methodology standards.

• Duration of Daylight/Darkness Table for One Year; U.S. Naval Observatory; accessed Aug 24, 2026