A lot of things about the zodiac can be more easily grasped by looking at a regular analog clock. The short, hour hand is the Sun. The long, minute hand is the Moon. whole clock is the zodiac. The Sun (short, hour hand) goes around the zodiac once, meanwhile in that time the Moon (long, minute hand) goes around 12 times. We put a tickmark at the hour hands position each time the minute hand completes a loop, and thus we have 12 hours. Similarly we put a tick mark in the zodiac each time the moon completes a loop and these tick marks define the boundaries of the 12 signs of the zodiac.