User blog comment:Kogath/Monster Hunter 4 Ultimate for the Nintendo 3DS/@comment-6050823-20140606010041/@comment-1758220-20140606010403

Well, back in MHFU, they retconned FnH to have a night time, and it was an entire generation old. (That they didn't do this for any of the other 1st gen maps is too bad)

So I'd say it's likely they'll have the other maps be Day/Night as well.