birthday fever

(applies to certain people only) when a person you used to have a crush, situationship or any other type of romantic history's birthday comes up, you suddenly think about them and feelings reemerge. for some, these feelings dissipate again, but for some no. (only applies if you know this person's birthday)

example: I started thinking about Logan a few days ago and I thought I was over him, but turns out it was just birthday fever.