Why is the moon a good way to keep track of time?

Humans have probably always recognized certain cycles in the passage of time. Perhaps the most obvious is that of the moon. As the moon moves in its orbit around the Earth, a crescent of its illuminated face becomes visible. The crescent grows over a period of nights until the entire face can be seen. This is called ‘full moon’. The face then wanes until once more it can’t be seen from Earth. This cycle takes an average 29.530589 days. Most of the early calendars were based on this moon cycle, also known as a 'lunation'.It is a near perfect one.That's why people considered it as a good way to keep track of time.

i think so.. because the moon's orbit is as constant as the earth's orbit around the sun.. that's why both are being used as relevant to the measurement of time.