Why does the lunar calender change each year? Why isnt it constant?

Question

I am writing this after reading about the Muslim fasting month. The start of the month depends on the sighting of the moon. But this date is never the same. It always changes. It may be the 7th or 10th or even the 3rd of the next english month.

My question is Why? Why does this change? Why does the lunar calender change? Its not like the moon slows down or something. So what is it?

In: Other

Answer 1

Lunar calendars don’t sync up with the Gregorian calendar, as 12 lunar cycles ends up being 11 days short of a sidereal (365.25 day) year.