Every Character in Stardew Valley has a birthday, EXCEPT the player character. I think a simple but good addition to the game would be to choose a day to be your birthday when you start a new game. NPC's you're friends with could then offer you birthday gifts and such.
There is a mod that does this, if you're interested. https://www.nexusmods.com/stardewvalley/mods/520 I found some of the gifts to be a little OP, such as when I received two prismatic shards when I first tried the mod a long time ago, but the gifts can be edited.
It's like if nobody wanted you in stardew valley, it's something basic that is needed (how to dance and dress the floral dance correctly lol)