:| Like that's hard to duplicate. It's probably fanmade, the year is included in the date, which none of the other ones have.
It's true I thought that suspicious at first, but on the other hand it seems just as likely that Namco could have made such a "mistake".
And Takagi did have a birthday banner this year, so why not also last year.
EDIT: Ah, Suika-san already proved it.