Fantasy Tropes/Cliches that Annoy You

[Deepbluediver]

One of my biggest pet peeves.
Evenly Divisible Base 10 Numbers and Societal Constructs as Cosmic Time Limits: The artifact works for 1 hour. The prophecy will be fulfilled in one thousand years. The portal activates for one week, every fifty years.

To be fair, things like day, month, and year can all have very definite non-arbitrary time periods. And some of the other stuff, like missing the ritual because of day-light savings time is the kind of thing I wouldn't expect to show up in a story unless it's a comedy.

But I do get your point, and I'd love to pull something like this on a group. Have a full moon only happen every 6 months or conversely have it happen every 6 days, or have prophecies demarcated in other counting systems.