Yes, this has been standardized in the Gregorian calendar.
December always has 31 days.
December always has 31 days.
yes
There are 31 days in December.
31
31
March always has 31 days.
There were 31 days in December 2007.
There were 31 days in December 2010.
There were 31 days in December 2004.
Well maybe, there was a mistake in printing it or some other reason. Just remember that December always has 31 days.
September has 30 days. December has 31 days