there is this tumblr i just stumbled upon that listed almost all characters possible and posted the birthday posts for every day.
Hello and welcome! This blog is dedicated to daily posts celebrating the birthdays of characters from anime, video games, visual novels and the like. I have a pretty huge log of fictional birthdays that I’m constantly adding to, so if you want to make sure I have the characters from a specific series on my list, let me know! This blog will update daily at noon.
Birthday Posts Only (no mod posts/asks)
Mod Kou: celesgami
series included in the birthday database (check here before suggesting a series to add!)