A full Gregorian cycle lasts 400 years, and interestingly, common years (i.e. those with 365 days) beginning on a Tuesday or Thursday are slightly more frequent than common years beginning in other weekdays. (44 vs. 43 for other weekdays) In leap years, 15 begin on a Sunday or on a Friday, 14 begin on Tuesday or Wednesday and 13 begin on a Saturday, Monday or Thursday.
And if you are wanting to know the frequency of specific days falling on a certain weekday: it’s between 56 and 58 times on a full cycle, depending of the year type. E.g. October 19 falls on a Saturday in 57 years of a full calendar cycle, but 58 years have it falling on a Monday and 56 years have it falling on a Tuesday.
It’s just me or is the Gregorian calendar very weird?
Have you been listening to the podcast A Problem Squared? This was a topic of the most recent episode (095 = Friday Fears and Disco Spheres). Friday the 13th is very slightly more common than other weekdays for the 13th.
https://aproblemsquared.libsyn.com/website/2022/04