I think dates for anime products should only be month, year
you could ask why?
the reason is when an anime starts broadcasting (for the first time) it's generally not broadcast on one channel but on several channels
so, of course, in a certain way, the first date to put will be logically the one of the first airing
but since there are several airing dates per anime broadcast (it usually starts at the beginning of a month), I think it could be better (or fairer) to avoid one date over all other ones, no?