A recent plaint from Aric Olnes (who is now 51) on Facebook:
Ugh. That moment when a retailer automatically spits out post-transaction coupons for Centrum Silver and laxatives! WTH, fifty is fifty! Sigh. Damn you, Walgreens.
Fifty is a cut-off point (at least in the U.S.) for the seque from middle age (beginning at 40 or 45, depending on who you read) to senior status (entered at 60-65, depending on who you read). There are “50+” organizations of many types, and the AARP takes members beginning at 50 — so it’s clearly not literally an association for retired persons (instead, it provides a kind of anteroom to retirement and true senior status).