<P> This sequence, given here for 1900--2099, 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, 2015 or 2026) (D), or January, April and July in a leap year starting on Sunday (such as 2012) (AG). </P> <P> The longest period that occurs without a Friday the 13th is 14 months, either from July to September the following year being a common year starting on Tuesday (F) (e.g. 2001 / 02, 2012 / 13 and 2018 / 19), or from August to October the following year being a leap year starting on Saturday (BA) (e.g. 1999 / 2000 and 2027 / 28). </P> <P> The shortest period that occurs with a Friday the 13th is just one month, from February to March in a common year starting on Thursday (D) (e.g. 2009, 2015 and 2026). </P> <P> Each Gregorian 400 - year cycle contains 146,097 days (with 97 leap days) or exactly 20,871 weeks . Therefore, each cycle contains the same pattern of days of the week and thus the same pattern of Fridays that are on the 13th . The 13th day of the month is slightly more likely to be a Friday than any other day of the week . On average, there is a Friday the 13th once every 212.35 days, whereas Thursday the 13th occurs only once every 213.59 days . </P>

Where did the origin of friday the 13th come from