According to the search results, a month has a Friday the 13th if and only if it begins on a Sunday. 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. The months with a Friday the 13th are determined by the Dominical letter (G, F, GF, etc.) of the year. In the original Friday the 13th movie, the date is not explicitly mentioned, but the opening credits read "Friday, June 13: The Present".