EpochLab

Night Length Calculator

How long is the night?

Darkness for any place and date — from sunset to sunrise, and separately the true astronomical night, which at high latitudes disappears entirely in summer.

Questions people ask

The things that come up about night length calculators, answered plainly.

What is astronomical night?

The period when the sun is more than 18° below the horizon and the sky is as dark as it gets. Above about 49° latitude it disappears entirely around midsummer — which is why northern Europe has no truly dark sky in June.

What are white nights?

The summer weeks at high latitudes when twilight lasts all night and the sky never goes fully dark. St Petersburg at 60° north is the famous case; the page will show it as astronomical night of zero length.

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Sunrise, sunset, the golden hour and the phase of the moon, anywhere on Earth.

Day Length CalculatorHours of daylight for any place and date, how much it changed since yesterday, and the longest and shortest days of that year at that latitude.
Sunset CalculatorSunset for any place and date, the twilight that follows, the bearing it goes down on, and how long you have before it is properly dark.
Blue Hour CalculatorThe window before dawn and after dusk when the sky is deep blue and lit buildings balance it — the sun between -6° and -4°, twice a day.
Moonrise CalculatorMoonrise for any place and date, with the phase and how much of the disc is lit — and an honest answer on the days when the moon does not rise at all.

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