mean solar time

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Time measured with reference to the mean sun so that each day of the year is exactly 24 hours long. Mean solar time differs from solar time since the earth's orbital speed, and therefore the length of the solar day, changes with the seasons.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (astronomy) time based on the motion of the mean sun (an imaginary sun moving uniformly along the celestial equator)