How to use this tool
- Choose a place and a date. The top card shows the day length on that date, how much it changes per day, and the longest and shortest days of the year.
- Read the curve. The first chart shows the number of hours of daylight for every day of the year.
- Read the daylight chart. The second chart shows when during the day there is daylight and twilight, for every day of the year.
- Compare. Add a second place to see the difference between, for example, your home and a holiday destination.
Why day length changes
Day length changes through the year because Earth’s axis is tilted by about 23.4°. In summer your hemisphere leans towards the sun, so the sun rises earlier, climbs higher and sets later. The further you are from the equator, the bigger the difference: at the equator days are about 12 hours long all year, at 50° N they range from about 8 to more than 16 hours, and beyond the polar circles there are days without sunset or sunrise. The guide why days are longer in summer explains the geometry.
Reading the charts
- Day length curve: one line per place, hours of daylight on the vertical axis. The dashed marker shows the selected date.
- Daylight chart: time of day runs from top (midnight) to bottom (midnight). Daylight is light yellow, the three stages of twilight are the blue shades. The steps in spring and autumn are daylight saving time changes.
- Sun height at noon: how high the sun climbs at solar noon each day. It matters for shade, solar panels and how strong the sunlight feels.
Worked example
Ljubljana (46° N) gets about 15 hours 46 minutes of daylight on the June solstice and about 8 hours 38 minutes on the December solstice, a difference of more than 7 hours. Around the March equinox, the days grow by about 3 minutes 15 seconds per day. Reykjavik (64° N) gets about 21 hours of daylight in June and only about 4 hours in December.
Twilight adds light
Day length counts only the time between sunrise and sunset. Civil twilight adds usable light before sunrise and after sunset: about half an hour at each end at mid-latitudes, and much more at high latitudes in summer. See twilight explained.
Last updated September 23, 2026