Those that have their birthday in months that aren't included can have an event after the main story after all P4 skips how much straight to Christmas and new year and then to April. The event days can work without a problem. If it's like P3 that most of the serious stuff happen at night they can just add some sort of celebration during the day and if it's during the day like P4 they can have it at night. It's not that important but I think it'd be a fun detail to add to the game, more so since the MC is suppose to be "you". Though even if they don't do any of that stuff I hope they at least add a birthday for the MC that they celebrate for example with a gf kinda like the Christmas event.