Are sunrise/sunset times when the sun starts setting and rising or when it is actually up and completely dark?

Question

I guess I'm more interested in sunset time. To be more specific lets say the almanac posts the sunset time to be 830pm. is 830 pm when the sun begins to go down or is it dark at 830 pm? Thanks in advance for any help.

Answer 1

Sunrise and sunset times are calculated for the time the sun actually breaks the horizon, based on longitude and latitude. In a mountainous region, you may see the sun earlier or later due to the landscape, but the time is set for where you are on a map, not your surroundings, and assumes a clear horizon.

Answer 2

When they mention sunrise and sunset, they are referring to when the sun either vanishes from site of the horizon or appears on the horizon of a flat surface, like the ocean.

Answer 3

I would say when it begins, for sunrise.

But when they give you time for sunset they mean when it gets dark i.e. no more sunshine...

Answer 4

Here is the definition of sunrise/sunset from the people who should know. The U.S. Naval Observatory which is charged by congress to calculate the official sunrise/sunset times.

"Sunrise and sunset conventionally refer to the times when the upper edge of the disk of the Sun is on the horizon, considered unobstructed relative to the location of interest. Atmospheric conditions are assumed to be average, and the location is in a level region on the Earth's surface."