What is the 28.5 day moon period?

Answer:
There really isn't one.

-- The moon completes one orbital revolution around the earth, and
one spin on its own axis, in 27.32 days.

-- Seen from the earth, the moon displays one complete cycle of phases
in 29.53 days.
First answer by Alcohen2006. Last edit by Alcohen2006. Contributor trust: 1145 [recommend contributor recommended]. Question popularity: 2 [recommend question].