In German, wishing someone a happy birthday is exactly that, which is why it's done in Accusative. So it would be "Fröhlichen Geburtstag" or "Frohen Geburtstag", having been abbreviated from "Einen fröhlichen Geburtstag".
[deleted] M
1 up, 3mo,
1 reply
Ah my mistake
I'm still struggling with die das der and den 😭🙏