First we should know what date/season it is (first the revelation before perhaps some event with birthday), now for some reason it's still a big unknown I don't think it's that close to happening.
Ami and Niki should know that date but for some reason they don't seem or want to bring it up, and I think it won't be a nice thing to say, quite possibly Akira's birthday is related to not so pleasant memories with Saki/Sekai, there are many references to birthday parties through happy events and sexual/traumatic events/blackouts.
Definitely if Sekai
gave some gift or celebrated a birthday to Akira, nothing to think about, memories of that, in this state it would be the final dagger.