Thread:Young Mako/@comment-26091443-20191007185156

So I'm not going to change it back, but I do feel the need to point out that if it's very literally the first day of the New Year, Izuku might just not know Hawk's birthday.

That strikes me as more likely than Horikoshi not understanding the flow of time or remembering the birthdate he set. Because again, we know his birthday, and we know for a fact that day has gone by.

But, again, I won't change it myself.  