It’s common knowledge that you can collect Social Security retirement benefits as early as when you turn 62. Only one problem: That generally isn’t the case. Only about 7% of people can get a check for the month they celebrate their 62nd birthday. The earliest starting point for the vast majority of retirees is age 62 and one month—even though financial advisors, journalists and, yes, the Social Security Administration regularly talk about what you could collect at age 62. And while it sounds like a small thing, that timing wrinkle affects how much your benefit could be reduced from what you would get at your full retirement age (or FRA). Let’s say you were born in 1960 or later, which means your FRA is 67. If you are among the few people who could start right at 62, and you decided to do so, you would get 70% of your full monthly benefit. More likely, no matter how big a rush you were in to start collecting, you’d begin a month later, taking 70.4% of your full benefit the month after you reached 62. (Of course, it’s often a wise move to delay the start of benefits to at least your late 60s. Read a few free ways the Social Security website can help you make that decision.) Read more: How to Navigate Social Security’s New Math Two Quirks What’s going on here? Credit two quirks in the way Social Security does its math. First, you have to be 62 for the full month to collect a benefit for that month. If you celebrate your 62nd birthday on Jan. 15, say, you clearly aren’t 62 for the full month of January. The earliest you could start benefits is for the month of February, when you will be 62 and one month old. And second, “Social Security has an interesting way of determining when you reach your next age,” says Gail Buckner, a vice president for Franklin Templeton Investments. “In Social Security Land, you actually reach your next birthday 24 hours before the day you were born.” That means–for those Jan. 15 babies–Social Security says you reach your new age on Jan. 14. So who gets to collect a Social Security benefit for the month that includes their 62nd birthday? One simple answer: anyone whose birthday is the second day of the month. Say you were born on Feb. 2, 1960 — which means you’ll blow out 62 candles (or one symbolic candle to represent your 62 years) on Feb. 2, 2022. Social Security will say you reached 62 on Feb. 1, and that means you will be that age for the full month. You could start benefits with a check for February, at the 70% payout. Then there’s a not-so-simple second group: people whose birthday is on the first day of the month. If your 62nd birthday is Feb. 1, 2022, Social Security will say you reached 62 on Jan. 31; you are clearly 62 for all of February and can get a check for that month. But here’s the added brain twister: Since Social Security considers your birthday to have been Jan. 31, the benefit you start in February will be at the reduction for 62 years and one month–i.e., the 70.4% level. Social Security’s operations manual for employees includes a four-page guide to How the Day of Birth Affects Benefits, notes James Mahaney, a Social Security specialist at Prudential Financial. Mahaney says he had no idea of the age-62 complexities until he started a deep dive into Social Security’s rules and the claiming strategies that people should consider. Now, the Prudential Social Security guide he wrote states that “most individuals are first eligible for their worker benefit at age 62 and one month.” One last factoid: Social Security benefits are paid the month after they are due, on a set schedule based on the day of the month you were born. So expect to receive your first payment the month after the period it is for.