My company give everyone the day off on their birthday, but only if your birthday is on a weekday, so some years you wouldn't get the extra day. But, my birthday is boxing day, so the office is always closed then! Which means I will never get an extra day and have 1 day per year less than everyone else. Am I wrong to feel a bit miffed?
No you are not wrong to be miffed and I would raise it.
I have only worked at one place where they had the birthday leave day and it was possible to take it any day that month. It is very surprising that management have not noticed how unfair their policy is.