As fun as I think Friday the 13ths are, its a social thing. There is generally no seasonal nor celestial event it coincides with. There is no actual non social significance to it. Our calendar system we use today is completely constructed, there is no inherent Fridayness.
Our calendar system is Roman. The months October, November and December mean 8th month, 9th month and 10th month. Two prideful emperors Julius and Augustus wanted months named after themselves, but not shitty cold months at the end of the year, pretty warm harvest months during the summer. And no ones months could be longer than theirs. So they were like July and August 31 days each, and who cares that it makes no sense for the 10, 11th and 12th months to mean 8 9 and 10.
To even better make the 12 month system work they had to add in leap years and do all sorts of other adjustments at different time periods. Lets not even get into alternate calendars and what day it is in Australia right now.