If February starts on a Sunday, Valentine's Day, February 14 will always occur on a Saturday. It is always exactly two weeks after the beginning of the month.

Normally, if February starts on a Sunday, March will also start on a Sunday, since February normally has 28 days. However, in a Leap Year, February has 29 days, so March will begin on a Monday

Easter falls on the first Sunday after the first full moon that occurs on or after March 21 and Fat Tuesday occurs 47 days before Easter, so it is dependent on the full moon and is not related to calendar dates.

In 2015, February started on a Sunday and it was NOT a Leap Year

More Info: en.wikipedia.org