Civil twilight
The Sun’s center is between the horizon and 6° below it. The table gives the morning start and evening end at −6°.
Nautical twilight
The Sun’s center is between 6° and 12° below the horizon. The −12° crossings mark nautical dawn and dusk.
Astronomical twilight
The Sun’s center is between 12° and 18° below the horizon. The −18° crossings mark the boundary used here for astronomical night. Some boundaries do not occur at high latitudes in summer.
Is dawn sunrise or sunset?
Dawn is the morning twilight that comes before sunrise; dusk is the evening twilight that follows sunset. Neither is the moment the Sun crosses the horizon. In everyday speech “dawn” usually means civil dawn, when there is enough light for outdoor activity without artificial lighting, and “dusk” means civil dusk. The result panel lists all three morning boundaries, then sunrise and sunset, then the three evening boundaries, in the order they happen.
When a boundary is missing
At high latitudes in summer the Sun may never sink to −18°, −12° or even −6°. The sky then stays in some stage of twilight all night, and the corresponding cells read Unavailable. During polar day or polar night sunrise and sunset are missing as well. Nothing is replaced with midnight or an estimate; the methodology page explains why.
Why twilight lengths differ
Twilight lasts as long as the Sun takes to travel through the band below the horizon. Near the equator the Sun’s path meets the horizon steeply, so twilight is brief. At high latitudes the path is shallow and twilight lingers, which is why summer evenings stay bright for so long in northern Europe. For the total hours of daylight between sunrise and sunset, use the day length page.