How does the moon change its phase?
New moon to New moon takes 29.53 days. During this time the moon
goes through several phases;
(New moon)
Waxing crescent moon
(First quarter moon - half moon)
Waxing gibbous moon
(Full moon)
Waning gibbous moon
(Last quarter moon - half moon)
Waning crescent moon
(Dark moon)
So roughly 7.5 days between each; New-half, half-full,
full-half, half-new.