A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robert VanderPol II
Date: 2015 May 13, 10:41 -0700
Time is measured based on the movement of the sun in the sky.
The moon is moving in the sky relative to the sun. Because the moon moves at an appreciable rate (12-13 degrees per day) a 30 degree change in longitude will change moon rise or set times by about 4 minutes. In the time the earth spins that far (about 2 hours) the moon will have moved 1 degree against the background.
If time were measured against the movement of the moon then longitude would need to be taken into account to deteremine rise and set times for the sun but not the moon.