My son H doesn't like his biological birthday, so a couple of years ago he appointed 12th October as his official birthday. This took some getting used to. I was worried that come his bio birthday he would be unhappy at not getting a present from me. Anyway we managed to divide up into the people who agreed to go along with it and those like me who preferred to give a present on the anniversary of his birth.
This time I was more content with the idea and while he was asleep went into his room to attach a big Happy Birthday banner right across the walls. I made a little heap of presents and cards too.
When I woke him in the morning he smiled the largest smile ever, a wonderful beam of joy and surprise on seeing the banner.