Why the Sun rises and sets at different times

Sunrise and sunset are the most predictable events in astronomy and, at the same time, the most often misunderstood. "The Sun rises in the east" is true, but it rises exactly due east only twice a year. The rest of the time the rising point drifts along the horizon, and the size of that drift depends on latitude more than on anything else.

The three things that set the time

Latitude. The closer to a pole, the longer the summer day. On the equator the difference between the longest and shortest day is about 15 minutes. At 60° north it is roughly 5 hours. Inside the polar circles there are summer days when the Sun does not set at all.

Season. Season works through the tilt of the axis, not through distance. The distance varies by 3%, which is nearly invisible in day length, whereas the 23.4° tilt makes a noticeable difference.

Longitude. A shift of 15° of longitude shifts local time by a full hour. That is why sunrise in Kaliningrad and in Moscow differ more than latitude alone would explain.

How the time is calculated

The calculation works from the Sun's altitude above the horizon at a chosen moment: standard sunrise and sunset are the moment the centre of the solar disc crosses the horizon, roughly −0.833°, accounting for refraction and the radius of the Sun. That is where the few-minute differences between tables come from — some count the upper edge of the disc, some the centre, some account for local terrain.

The table on the city page gives local solar time for that city, not your own time zone.

Twilight

Civil twilight is the interval when the Sun is between 0° and −6°: the day is over, but the landscape is still visible. Nautical twilight runs to −12° and astronomical twilight to −18°. The higher the latitude, the longer twilight lasts in summer, because the Sun sets along a shallower path and stays low for longer.

Why it matters

If you are planning a shoot, an observation session, or simply want to know when it is comfortable to be outside, twilight is more useful than sunrise itself. And in winter at high latitudes the "daylight" window is short enough that planning around sunrise rather than the start of morning twilight is the better habit.