Leap year starting on Monday
A leap year starting on Monday is any year with 366 days (i.e. it includes 29 February) that begins on Monday, 1 January, and ends on Tuesday, 31 December. Its dominical letters hence are GF, such as the years 1912, 1940, 1968, 1996, 2024, 2052, 2080, and 2120 in the Gregorian calendar or, likewise, 2008, 2036, and 2064 in the obsolete Julian calendar. 
Any leap year that starts on Monday, Wednesday or Thursday has two Friday the 13ths. This leap year contains two Friday the 13ths in September and December. Common years starting on Tuesday share this characteristic.
February
February is also the only month of the calendar that, once every six years and twice every 11 years consecutively, either back into the past or forward into the future, has four full 7-day weeks. In countries that start their week on a Monday, it occurs as part of a common year starting on Friday, in which February 1st is a Monday and the 28th is a Sunday; this occurred in 1965, 1971, 1982, 1993, 1999 and 2010, and occur will again in 2021. In countries that start their week on a Sunday, it occurs in a common year starting on Thursday, with the next occurrence in 2026, and previous occurrences in 1987, 1998, 2009 and 2015. The pattern is broken by a skipped leap year, but no leap year has been skipped since 1900 and no others will be skipped until 2100.