what's a leap year
Every fourthyear is a leap year, as a rule of thumb. But that's not the end of the story. A year that is divisible by 100, but not by 400, is not. So 2000 was a leap year under the Gregorian calendar, as was 1600. But 1700, 1800 and 1900 are not leap years.
Monday is Feb. 29, making 2016 a leap year with February having 29 days instead of the more typical 28.