The equation of time, introduced by Ptolemy and later refined based on the work of Johannes Kepler, converts between apparent solar time and the mean time we've all come to rely on.

“均时差”概念，由托勒密发明后来由约翰尼斯·开普勒进行的改良，包含了太阳时间和平均时间的差距，是我们现在主要使用的时间概念。