Why twilight length varies
Near the equator the Sun drops almost vertically, so all three phases together take only about 70 minutes. At higher latitudes it sinks at a slant and twilight lasts longer; around midsummer north of about 48.5°N the Sun never gets 18° below the horizon, so astronomical night never arrives. Times are calculated in your browser from the Sun's position (the same method as NOAA-style solar calculators). They assume a flat horizon at sea level, so mountains, buildings and altitude can shift what you actually see by a few minutes.
Frequently asked questions
Is twilight before sunrise or after sunset?
Both. Morning twilight runs from astronomical dawn to sunrise, and evening twilight runs from sunset to astronomical dusk.
Which twilight is 'twilight' in everyday speech?
Usually civil twilight — the first half hour or so after sunset when it is still fairly light.
Why does the tool say the sun stays above −18° all day?
In summer at high latitudes the Sun doesn't sink far enough for astronomical night. Twilight then lasts from sunset until sunrise.
