That's right, because you should also enter the date of birth on the calendar.

Almost no such scenario comes to my mind, so that in the mail form you need to indicate your birthday, but the date of some upcoming event is constantly

The date field is supposed to be universal and if only 5% of users need a date of birth, then it's bad if you can't enter an earlier date.

So, you need to make a switch in the object with the ability to block the selection of past dates.