Our observing spot on Prince Edward Islands was half a mile from being exactly in line with the center of the 865,000 mile diameter sun and the center of the 2,100 mile diameter moon. Aside from the privilege of being in line with great celestial bodies, timing such events has practical importance. The timing of a star's appearance or disappearance at the edge of the moon from a known location on the earth is used to accurately determine the position of the moon. It takes many occultation observations of many stars by many observers to accurately determine the orbit and true motion of the moon. From observations like these astronomers found out that the moon kept a different time than the earth.
Earthly time is based on the rotation of the earth.
But, it turned out that the earth is slowing down. So time based on that changing rate cannot be used for time based position calculations of the sun, moon and planets. Atomic clocks are also immune to the earth's slowing rotation. Now, atomic time has become the basis for earthly time. So to keep our clocks a tuned to the sun via the earth's rotation, an occasional leap second is added at approximate 18 month intervals.