Cutting your hair during a full moon will not make it grow back faster
The moon's gravitational force causes the tides, but has no effect on hair growth.
A popular myth claims that hair grows back faster during a full moon. This is a myth that's probably based on the moon's influence over the oceans that causes high or low tides depending on the positions of the moon and the sun. These gravitational forces are infinitesimal for light-weight matter and can of course have no influence on hair growth.