Annual Day Length Calculator
Day & night length by latitude
📊 Day Length by Month (Jan–Dec)
Yellow curve = day length, dashed = 12h. Vertical line = today.
Today
Day
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Night
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✨ Special Days
| ☀️ Longest day (summer solstice) | - |
| 🌙 Shortest day (winter solstice) | - |
| ⚖️ Day = Night (12h each) | - |
※ Sunrise/sunset times appear once a location (longitude) is set. The 'day = night' date differs from the equinox by a few days due to refraction (equilux).
⚠️ Location is used only for lookup and is not stored. Altitude and temperature are reference estimates from standard models and may differ from reality. calcstool.com assumes no liability.
FAQ
Can latitude alone predict day length?
Yes. Day length depends on latitude and date (the sun\u2019s declination). With your latitude, the whole year can be computed. Longitude and timezone do not affect day length itself.
When are the longest and shortest days?
In the northern hemisphere the longest day is the summer solstice (around June 21) and the shortest is the winter solstice (around Dec 22). Higher latitudes have a bigger difference.
Why does day = night differ from the equinox?
Atmospheric refraction. Light bends through the atmosphere so the sun appears to rise earlier and set later, making the 12-hour day (equilux) fall a few days before or after the equinox.
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