If a month starts on Sunday, it will have a Friday the 13th.

This sequence given here for 2001–2028, follows a 28-year cycle from 1 March 1900 to 28 February 2100. The months with a Friday the 13th are determined by the Dominical letter (G, F, GF, etc.) of the year. Any month that starts on a Sunday contains a Friday the 13th, and there is at least one Friday the 13th in every calendar year. There can be as many as three Friday the 13ths in a single calendar year; either in February, March and November in a common year starting on Thursday (such as 2009 or 2015) (D), or January, April and July in a leap year starting on Sunday (such as 2012) (AG).

@Curionic

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