My friends know, and we usually get together and play games on a day designated as my birthday. It’s usually on the weekend before or after the actual day. As for remembering, if you know someone well enough to be present at their birthday, just write it down. You all have phones, don’t you? Honestly though, the older I get, the less it has mattered. It’s really just an excuse for us to get together. My wife gets me something sweet (usually a cinnamon roll), everyone sings “happy birthday” and we go back to whatever game is on the table. It’s nice to be thought of, but mostly I just want to be with friends and family.