Noun
equation of time (plural equations of time)
The discrepancy between two kinds of solar time: the apparent solar time, which directly tracks the motion of the Sun, and mean solar time, which tracks a theoretical "mean" Sun with noons 24 hours apart.
As the variation accumulates over a few weeks, there are differences as large as 16 minutes between apparent solar time and mean solar time (see Equation of time ). Source: Internet