Triskaidekaphobia: fear of the number 13
I’ve known many people with an aversion to this perceived “unlucky” number, whether serving as a date of particular significance or - the more common superstition - when it should happen to fall on a Friday, of all days. Personally, I’ve taken special care to note any particularly negative occurrences on these infrequent juxtapositions of day and date, with thankfully few to report. Just another day, as they say.