It is the day that causes dread in people who believe in it. Two different phobias that drive superstitions - the fear of 13 (triskaidekaphobia) and the fear of a particular day as a fearful day (paraskevidekatriaphobia) - two hugely unpronounceable words that I struggled with.
I also saw an interesting movie describing the phenomenon while catching up on the BBC News this morning.
https://www.bbc.com/reel/video/p0jq8p89/friday-the-13th-the-psychology-behind-the-superstition
It helped me learn that the fear of 13 comes from the people in the “Last Supper” and the author who further articulates:
Why do we believe in it? Magical thinking is probably rooted in our evolutionary biology. It had, and perhaps still does have, positive functions. It's a confusing, complex, unpredictable world that we live in. Magic gives the individual a sense of control - that 'my little part of this cosmos can be somehow shaped and controlled at least right now.'
They might not like to call it magic, but that's really fundamentally the way people think.
Fascinating isn’t this, our species called “Humans”. Enjoy it as I truly did.