I've worked in the same company for 8 years, nearly everyone there is there longer than me. There's always been a collection for big birthdays, about 15 staff members, which I've always contributed to. Now my 40th birthday is coming up and I've never mentioned my date of birth before as it's never come up, so no one knows I'm going to be 40 or even that it's my birthday. It might seem silly and childish but I feel I'm missing out as I've always contributed to others' birthdays.
AIBU - Say nothing
AINBU - drop it into conversation (but don't know how!)