Day length
Updated October 15, 2026.
Day length is sunrise to sunset. The page rounds each clock to the nearest minute and reports the span the same way, in hours and minutes. Dawn, dusk, first light, and last light are outside that span. Adding them would describe twilight plus daylight, which is a different number and is not what the line means.
The length changes through the year. In the northern hemisphere the longest days are around the June solstice and the shortest around the December solstice. The change is fastest around the equinoxes, when the day can gain or lose a couple of minutes every calendar day. Two stations at different latitudes do not share a day length even when they share a time zone. The sun time is computed for that station's latitude and longitude.
Clock time and sun time
Daylight saving changes how the hours sit on the clock. It does not change how many hours the sun is up. A 14-hour day in July is still 14 hours after you read it in local time. Solar noon sits in the middle of that span. If you split the day length in half and walk back from sunset, you land near solar noon. Walking back from last light will not, because last light includes twilight the day length ignores.
The number is a description of that date at that coordinate. It is not an average, and it is not the photoperiod used in a biology paper unless that paper also means sunrise to sunset. When the sun service does not answer, the page calculates sunrise and sunset and subtracts them. The label stays "Day length" either way.