mean solar time

Due to the earth's elliptical orbit, the sun can be as much as 16 minutes out of line with mean solar time.

Does air traffic control have embedded assumptions about mean solar time or Earth orientation?

The difference between the corrected time and 12 o'clock will be the correction of your watch referred to local mean solar time.

In the 17th century it was a favourite device to make a clock show sidereal time as well as mean solar time.

The Earth accomplishes a revolution on its axis in 23 hours 56 minutes 4 seconds mean solar time, which is the length of the sidereal day.