# Another "settle an argument" thread \[calculating someone's age on a particular date\] **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [October 28, 2026, 5:52pm UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220 "2026-10-28T17:52:20Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [October 29, 2026, 3:07am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/21 "2026-10-29T03:07:10Z")
I concur with everyone else, of course: 25 and 23. I could see the two of them rounding up if they really wanted to, but it would be seen them fudging a bit. It’s a silly thing I’ve noticed. Whenever we are being precise about time, we round down. If we’re waiting 12 minutes, we don’t call it at 11 minutes 59.5 seconds. You have to above 12 minutes. Same with 10 seconds. Or talking about when it is actually midnight. It is not your birthday until after midnight. You aren’t one year older until after the time has elapsed. Not a day earlier. Not a month earlier. And definitely not two or three months earlier. ---
**Author:** ![CairoCarol](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cairocarol/32/3825_2.png) [@CairoCarol](https://boards.straightdope.com/u/CairoCarol)\ **Post date:** [October 29, 2026, 3:48am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/22 "2026-10-29T03:48:25Z")
Thanks everyone. The story behind the disagreement is pretty boring. We were talking about our son, who is 28, unmarried, and at the moment has no girlfriend (though he has had a couple of long-term relationships in the past). He is a snuggly guy and would love a permanent relationship. (Why he isn’t in one is a subject for another day, or thread.\*) I said something along the lines of “I wouldn’t want CairoSon to be depressed because he is 28 and single, and his parents got married at ages 23 and 25.” At which point Mr. Cairo says, “oh no, we were married at 24 and 26.” (In fact, with a few changes to make the example simpler/starker, we were married as described in the OP.) Mr. Cairo always rounds up everything. Which makes sense in some situations, but I don’t know why the hell you’d round up your age. My argument to him was: Look, you will be age X for 12 months no matter what. If you start using a rounding rule, you’ll just state your age for a slightly shifted 12-month period. So why not count like people generally count people’s ages? If you die in a car crash when you are 48 years and 11 months old, the newspaper article about the crash is not going to ID you as 49. It will say you were 48. Mr. Cairo’s response was, “well, but that’s how most people do it” (meaning everyone rounds up). I disagreed, claiming most people (Americans, anyway) do NOT round up. According to me, the American standard is this: when you are 53 years, 11 months, and 27 days old, you are 53. You turn 54 ON YOUR BIRTHDAY. He eventually conceded that he wasn’t really sure how most people characterize their age, so agreed to having me ask Dopers, in case he was wrong and his rounding up is atypical. Thank you all for your input. I feel vindicated. \*Any of you with most excellent mental catalogs of Dopers will also wonder about the inconsistency between [this thread](https://boards.straightdope.com/t/fessing-up-to-my-divorce/831800/18) and what I’m posting here, which is also a long story for another thread. Suffice it to say things changed. All is well in my life now. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [October 29, 2026, 4:31am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/23 "2026-10-29T04:31:24Z")
> [@Eyebrows\_0f\_Doom](#): > > 23 and 25. How is this even a debate? It is not a “debate”, exactly, but… For instance, in Korea, when you are are born, your age is 1, right? And it increments on January 1st, not on any other day, right? If all of that is not obvious and does not go without saying, then you have to admit that someone’s “age” is not clear-cut. > [@CairoCarol](#): > > According to me, the American standard is this: when you are 53 years, 11 months, and 27 days old, you are 53. You turn 54 ON YOUR BIRTHDAY. If distinctions like this are important, you may need to consult a local contract lawyer rather than take legal advice from people on the Internet.. ---
**Author:** ![don\_t\_ask](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@don\_t\_ask](https://boards.straightdope.com/u/don_t_ask)\ **Post date:** [October 29, 2026, 5:57am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/24 "2026-10-29T05:57:33Z")
According to Mr Cairo’s method you have your 21st on the last day that you are 21. And how does his method hold up with the legal drinking age? “Honestly officer, everyone is 21 the day after they have been alive for 20 years.” ---
**Author:** ![ricepad](https://avatars.discourse-cdn.com/v4/letter/r/b38774/32.png) [@ricepad](https://boards.straightdope.com/u/ricepad)\ **Post date:** [October 29, 2026, 6:42am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/25 "2026-10-29T06:42:39Z")
Thank you for explaining it. Mr. Cairo is right. Sort of. Everybody rounds their age up. Then they turn 10, and stop that nonsense, mostly. Some may persist for a few more years, but after that? Nope. ---
**Author:** ![CairoCarol](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cairocarol/32/3825_2.png) [@CairoCarol](https://boards.straightdope.com/u/CairoCarol)\ **Post date:** [October 29, 2026, 7:18am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/26 "2026-10-29T07:18:04Z")
> [@don\_t\_ask](#): > > And how does his method hold up with the legal drinking age? Hah! Why didn’t I think of that? I believe you have definitively resolved the argument. ---
**Author:** ![Q.Q.Switcheroo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/q.q.switcheroo/32/5713_2.png) [@Q.Q.Switcheroo](https://boards.straightdope.com/u/Q.Q.Switcheroo)\ **Post date:** [October 29, 2026, 7:57am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/27 "2026-10-29T07:57:14Z")
Then there’s the thornier issue of how to deal with a February 29 birthday: > **[Juvenile or adult? Leap-year suspect causes headache for court](https://www.abc.net.au/news/2018-09-13/canberra-court-leap-year-girl-adult-or-child/10242750)** > > A girl born on February 29, 2000, who allegedly broke the law on February 28 exactly 18 years later causes a conundrum for a Canberra court. Should she be treated as an adult? > The girl, who cannot be named for legal reasons, was being treated as an adult over offences allegedly committed on February 28, 2018. > > As there was no February 29 in 2018, the ACT Children’s Court initially found the girl had turned 18 on the day of the crime, and should be dealt with in the adult court system. > > But the girl’s lawyers applied for a review, arguing she should not be treated as an adult until March 1, 2018. (The court ultimately found she was still a child on the day of the crime.) ---
**Author:** ![Ancient\_Nerd](https://avatars.discourse-cdn.com/v4/letter/a/ed655f/32.png) [@Ancient\_Nerd](https://boards.straightdope.com/u/Ancient_Nerd)\ **Post date:** [October 29, 2026, 8:13am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/28 "2026-10-29T08:13:23Z")
> [@Q.Q.Switcheroo](#): > > no one calls a 22-month-old toddler “one year old” except to be willfully perverse. At young ages, we often use fractions. As I approached 9, I was 8 1/2. At the toddler level, we could go further with 1 3/4. We could even go for almost 2 or not quite 2. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [October 29, 2026, 12:47pm UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/29 "2026-10-29T12:47:46Z")
> [@CairoCarol](#): > > “well, but that’s how most people do it” (meaning everyone rounds up). I disagreed, claiming most people (Americans, anyway) do NOT round up. According to me, the American standard is this: when you are 53 years, 11 months, and 27 days old, you are 53. You turn 54 ON YOUR BIRTHDAY. UK standard as well. No rounding birthdays up. Personally, I tend to round other things up all the time. 11:55 is 12 o’clock, £9.75 is £10.00, and 4¾ miles is 5 miles ---
**Author:** ![doreen](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@doreen](https://boards.straightdope.com/u/doreen)\ **Post date:** [October 29, 2026, 12:51pm UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/30 "2026-10-29T12:51:38Z")
Depends on the purpose - for most purposes, if I’m asked, I will give my actual age. But sometimes I’ll be a little more detailed- I don’t round up, but if you ask how old my grandfather was when he died, my answer will be “the day before his 90th birthday” , not “89” ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 29, 2026, 9:53pm UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/31 "2026-10-29T21:53:17Z")
> [@Q.Q.Switcheroo](#): > > Then there’s the thornier issue of how to deal with a February 29 birthday: The exact same issue shows up for everyone else, too, except we usually ignore it for non-leap-babies. The actual resolution is to note time of birth as well as date, and then count integer multiples of 365.2425 days after that time. I wrote myself a simple little program to determine on what date (and time) the anniversary of my birth falls every year. Because it’s not always the same date. ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [October 29, 2026, 10:18pm UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/32 "2026-10-29T22:18:09Z")
> [@ricepad](#): > > Thank you for explaining it. Mr. Cairo is right. Sort of. Everybody rounds their age up. Then they turn 10, and stop that nonsense, mostly. Some may persist for a few more years, but after that? Nope. As my grandfather went from old to exceedingly old he started saying “I am in my XX year” rather than just “I am years old.” He very deliberately rounded his age up to appear even older - therefore more worthy of esteem - as someone in their 95th year compared to those 94-year old punks hanging out on street corners. (No, he was not senile, he knew damn well how old he really was.) The family flat out refused to entertain the notion that he should have an official 100th birthday party until he actually turned 100. But even after that when he turned 102 he STILL described himself as in his 103rd year. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [October 30, 2026, 11:52am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/33 "2026-10-30T11:52:10Z")
> [@Q.Q.Switcheroo](#): > > (The court ultimately found she was still a child on the day of the crime.) In dubio pro reo. ---
**Author:** ![Ancient\_Nerd](https://avatars.discourse-cdn.com/v4/letter/a/ed655f/32.png) [@Ancient\_Nerd](https://boards.straightdope.com/u/Ancient_Nerd)\ **Post date:** [October 30, 2026, 8:42pm UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/34 "2026-10-30T20:42:25Z")
A baby born on Dec. 31 could be in its second year at the age of two days. ---
**Author:** ![Q.Q.Switcheroo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/q.q.switcheroo/32/5713_2.png) [@Q.Q.Switcheroo](https://boards.straightdope.com/u/Q.Q.Switcheroo)\ **Post date:** [October 30, 2026, 9:03pm UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/35 "2026-10-30T21:03:41Z")
And a baby born in Samoa on January 1 who was transported to American Samoa later that day could enter its second year twice. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [October 31, 2026, 6:22am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/36 "2026-10-31T06:22:14Z")
The legal standard is just that you are definitely a year older on the day after your birthday, March 1. ---
**Author:** ![Lord\_Feldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lord_feldon/32/341_2.png) [@Lord\_Feldon](https://boards.straightdope.com/u/Lord_Feldon)\ **Post date:** [October 31, 2026, 7:38am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/37 "2026-10-31T07:38:53Z")
> [@doreen](#): > > But sometimes I’ll be a little more detailed- I don’t round up, but if you ask how old my grandfather was when he died, my answer will be “the day before his 90th birthday” , not “89” Under the old common law rule for determining ages, he really was 90, as he was alive on all 365 (or 366) days of his 90th year, and you didn’t have to finish the last one to legally attain the new age. Social Security still uses this rule to calculate ages. ---
**Author:** ![TokyoBayer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tokyobayer/32/13989_2.png) [@TokyoBayer](https://boards.straightdope.com/u/TokyoBayer)\ **Post date:** [October 31, 2026, 7:41am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/38 "2026-10-31T07:41:22Z")
> [@DPRK](#): > > For instance, in Korea, when you are are born, your age is 1, right? And it increments on January 1st, not on any other day, right? This has [changed](https://www.bbc.com/news/world-asia-66028606) as of 2023. > **South Koreans have become a year or two younger as a new law aligns the nation’s two traditional age-counting methods with international standards.** > > The law scraps one traditional system that deemed South Koreans one year old at birth, counting time in the womb. > > Another counted everyone as ageing by a year every first day of January instead of on their birthdays. > > The switch to age-counting based on birth date took effect on Wednesday. ---
**Author:** ![I\_Love\_Me\_Vol.I](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/i_love_me_vol.i/32/521_2.png) [@I\_Love\_Me\_Vol.I](https://boards.straightdope.com/u/I_Love_Me_Vol.I)\ **Post date:** [October 31, 2026, 9:00am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/39 "2026-10-31T09:00:40Z")
I bet many birthday cakes were sold that day as people kidded around celebrating their “new” age. ---
**Author:** ![Author\_Balk](https://avatars.discourse-cdn.com/v4/letter/a/e0b2c6/32.png) [@Author\_Balk](https://boards.straightdope.com/u/Author_Balk)\ **Post date:** [October 31, 2026, 11:20am UTC](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220/40 "2026-10-31T11:20:56Z")
Which got me thinking. I moved to a different time zone from the one I was born. What if I was born close to midnight. If I was born at 11:30 PM, it would be 12:30 AM the next day my current time. Should I change my birthday? If someone in a different time zone was watching the events of 9/11 on TV and it was a different date, couldn’t it be 9/10 or 9/12 for them? Or do you always go by the date of the the place where it happened? But, if we dropped a bomb on another country we probably would consider the date it happened for us. [Previous page](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220.md?page=1) [Next page](https://boards.straightdope.com/t/another-settle-an-argument-thread-calculating-someones-age-on-a-particular-date/1034220.md?page=3)