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.
Accounting period
The end of the fiscal year would move one day earlier on the calendar each year (two days in leap years) until it would otherwise reach the date four days before the end of the month (August 27 in this case). At that point the first Saturday in the following month (September 3 in this case) becomes the date closest to the end of August and it resets to that date and the fiscal year has 53 weeks instead of 52. In this example the fiscal years ending in 2011 and 2016 have 53 weeks.