It's already been answered, multiple times, Dumbass.

But lets take it s-l-o-w and in stages for your benefit.


♦ About 29½ days from one full Moon to the next.
♦ So a Full Moon can fall either 29 days or 30 days after the previous one, depending what time of day it occurs
♦ Calendar months can have 28, 29, 30 or 31 days
♦ Most calendar months are 30 days or 31 days
♦ Because lunar month is shorter than most calendar months, the DATE of full Moon will gradually work it's way forward from one month to the next.
♦ Sooner or later, Full Moon will fall in the first few days of calendar month
♦ When Full Moon occurs on 1st or 2nd, the next can occur on 30th or 31st - it's simple maths
VERY simple maths - you don't get much simpler than addition.