# Is 2/29 an invalid birth date? **URL:** \ **Category:** Factual Questions\ **Created:** [February 29, 2012, 6:18pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370 "2012-02-29T18:18:09Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [February 29, 2012, 9:40pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/21 "2012-02-29T21:40:17Z")
Everyone should switch to my calendar, in which the leap day is February 28b. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [February 29, 2012, 10:55pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/22 "2012-02-29T22:55:12Z")
To set my watch, I had to enter time, date, and year. It doesn’t display the year, but it didn’t surprise me in the least when I got up this morning and it was reading 2-29. Previous years it just gone to March 1 after Feb. 28. ---
**Author:** ![TBG](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@TBG](https://boards.straightdope.com/u/TBG)\ **Post date:** [February 29, 2012, 11:07pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/23 "2012-02-29T23:07:16Z")
> [@fiddlesticks](#): > > This is the top Google result for [leap day bug](http://www.rimmkaufman.com/blog/leap-day-bug/29022012/). So today is an invalid day to create a ads through the Bing system, apparently. Reminds me of 4 years ago when everyone’s Playstation 3 went apeshit because one of the internal calendars didn’t recognize 2/29 but something else on the system did. edit:whoop, my bad, it was because the system thought 2010 WAS a leap year when it wasn’t ---
**Author:** ![tellyworth](https://avatars.discourse-cdn.com/v4/letter/t/977dab/32.png) [@tellyworth](https://boards.straightdope.com/u/tellyworth)\ **Post date:** [February 29, 2012, 11:22pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/24 "2012-02-29T23:22:59Z")
For the most part, programmers shouldn’t be adding numbers to dates. They should be using date addition functions, which are widely available and carefully tested for all sorts of tricky situations like leap years and DST. They also usually require less application code than doing it the hard way. ---
**Author:** ![Mangosteen](https://avatars.discourse-cdn.com/v4/letter/m/6a8cbe/32.png) [@Mangosteen](https://boards.straightdope.com/u/Mangosteen)\ **Post date:** [March 1, 2012, 12:24am UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/25 "2012-03-01T00:24:44Z")
> [@Skammer](#): > > We’re celebrating my co-worker’s 14th birthday today. We were going to get her a Justin Bieber CD but her grandchildren said she wouldn’t like it. Dear old Dad turns 23 today. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [March 1, 2012, 5:58am UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/26 "2012-03-01T05:58:08Z")
> [@Chronos](#): > > On the other hand, you could also consider the birthday to be “the day before the 1st of March”. > > **Really, the cleanest (though not simplest) way to handle it is to call your birthday the day on which you are an integer number of years old. Take the date _and time_ of your birth, add some multiple of 365.242199 days, and see what date this falls on.** What most people don’t realize, though, is that if you do it this way, it actually affects the entire calendar, not just the end of February. For instance, about 3 years out of every 4 (including the year I was born), my birthday falls on April 29, but about 1 year out of 4, it falls on April 30. This, essentially. [**Cecil Himself**](http://www.straightdope.com/columns/read/1216/when-do-leap-day-babies-celebrate-their-birthdays) expounds. ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [March 1, 2012, 7:55am UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/27 "2012-03-01T07:55:41Z")
> [@robert\_columbia](#): > > This is a plot device in Gilbert and Sullivan’s The Pirates of Penzance. The Pirates of Penzance? I’ve often heard that. > [@naita](#): > > Everyone should switch to my calendar, in which the leap day is February 28b. Or the hobbit calendar, in which Mid-Year’s Day belongs to no week or month (and so every year has the same calendar) and nor does the leap day, which is called “Overlithe” and comes the day after Mid-Year’s Day. ---
**Author:** ![Diceman](https://avatars.discourse-cdn.com/v4/letter/d/22d042/32.png) [@Diceman](https://boards.straightdope.com/u/Diceman)\ **Post date:** [March 1, 2012, 12:56pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/28 "2012-03-01T12:56:20Z")
> [@robert\_columbia](#): > > This is a plot device in Gilbert and Sullivan’s The Pirates of Penzance. There’s also a Sherlock Holmes story that uses this plot device. This Scottish guy is 80 years old, but still hasn’t received an inheritance that he’s supposed to get in the year of his 21st birthday. Oh yeah, this takes place in the year 1900, which makes things even more messed up, because nobody remembers until the last minute that century years aren’t leap years. ---
**Author:** ![Frank](https://avatars.discourse-cdn.com/v4/letter/f/3d9bf3/32.png) [@Frank](https://boards.straightdope.com/u/Frank)\ **Post date:** [March 1, 2012, 1:34pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/29 "2012-03-01T13:34:55Z")
> [@Diceman](#): > > Oh yeah, this takes place in the year 1900, which makes things even more messed up, because nobody remembers until the last minute that century years aren’t leap years. While spending months coding Y2K changes, I asked my boss if I should add code to allow for that as long as I was there anyway. He said, “No, no one will be using this COBOL code in 2100.” They’re still using it today, so we’ll see. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [March 1, 2012, 1:43pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/30 "2012-03-01T13:43:01Z")
> [@Diceman](#): > > …Oh yeah, this takes place in the year 1900, which makes things even more messed up, because nobody remembers until the last minute that century years aren’t leap years. That’s usually true, but remember that in the Gregorian Calendar, century years that are divisible by 400 **are** leap years. So the year 1900 was not a leap year, but the year 2000 **was** a leap year. ---
**Author:** ![Chessic\_Sense](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@Chessic\_Sense](https://boards.straightdope.com/u/Chessic_Sense)\ **Post date:** [March 1, 2012, 1:43pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/31 "2012-03-01T13:43:31Z")
> [@Diceman](#): > > There’s also a Sherlock Holmes story that uses this plot device. This Scottish guy is 80 years old, but still hasn’t received an inheritance that he’s supposed to get in the year of his 21st birthday. > > Oh yeah, this takes place in the year 1900, which makes things even more messed up, because nobody remembers until the last minute that century years aren’t leap years. Say what, now? Every presidential election year is a leap year. Isn’t it? Is there some special break on century years? Edit: Just read the wiki and now **robby** ’s here to report the results. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [March 1, 2012, 1:52pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/32 "2012-03-01T13:52:29Z")
[QUOTE=psychonaut] But presumably the federal government didn’t issue his driver’s licence, so the OP’s scenario wouldn’t apply in this case. [/QUOTE] The federal government didn’t issue the license, but they [control just about every possible aspect of all states’ licenses](http://en.wikipedia.org/wiki/REAL_ID_Act#Federally_mandated_standards_for_state_driver.27s_licenses_or_ID_cards), other than the colors. The Department of State also has no problems whatsoever with 2/29 birthdays when they issue passports. As usual for talk radio, what the OP’s boss describes is utter bunk. ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [March 1, 2012, 1:53pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/33 "2012-03-01T13:53:51Z")
This has turned out to be much more interesting than I expected. But, buried in the OP, is a question; Does the federal government _require_ the parents to choose to enter either Februrary 28 or March 1, not Februrary 29 on the baby’s birth certificate? Seems to me that would be depriving someone born on that of a pretty unique document and a cool talking point. ---
**Author:** ![Skammer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skammer/32/143_2.png) [@Skammer](https://boards.straightdope.com/u/Skammer)\ **Post date:** [March 1, 2012, 2:07pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/34 "2012-03-01T14:07:45Z")
> [@Chronos](#): > > On the other hand, you could also consider the birthday to be “the day before the 1st of March”. > > Really, the cleanest (though not simplest) way to handle it is to call your birthday the day on which you are an integer number of years old. Take the date _and time_ of your birth, add some multiple of 365.242199 days, and see what date this falls on. What most people don’t realize, though, is that if you do it this way, it actually affects the entire calendar, not just the end of February. For instance, about 3 years out of every 4 (including the year I was born), my birthday falls on April 29, but about 1 year out of 4, it falls on April 30. And don’t forget to add/subtract hours if you were born in a different time zone. 😃 ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [March 1, 2012, 2:09pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/35 "2012-03-01T14:09:32Z")
> [@mangeorge](#): > > This has turned out to be much more interesting than I expected. But, buried in the OP, is a question; Does the federal government _require_ the parents to choose to enter either Februrary 28 or March 1, not Februrary 29 on the baby’s birth certificate? Does the federal government issue many birth certificates? That’s really the [province of the states](http://en.wikipedia.org/wiki/Birth_certificate#Birth_certificates_in_the_United_States). Perhaps on military base hospitals abroad? I’m not sure what standards apply there. U.S. territories seem to have their local territory government responsible for issuing birth certificates rather than the feds. ---
**Author:** ![fiddlesticks](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fiddlesticks/32/18129_2.png) [@fiddlesticks](https://boards.straightdope.com/u/fiddlesticks)\ **Post date:** [March 1, 2012, 4:02pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/36 "2012-03-01T16:02:00Z")
The [Geniuses at Microsoft](http://www.techweekeurope.co.uk/news/windows-azure-leap-year-glitch-takes-down-g-cloud-63920) had a Leap Year bug cause an outage for their Azure cloud service. /cue hooting from all the Apple & Linux fanboys and gurls. ---
**Author:** ![Bricker](https://avatars.discourse-cdn.com/v4/letter/b/977dab/32.png) [@Bricker](https://boards.straightdope.com/u/Bricker)\ **Post date:** [March 1, 2012, 4:04pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/37 "2012-03-01T16:04:04Z")
> [@Malacandra](#): > > The Pirates of Penzance? I’ve often heard that. Do you mean often, as in frequently? ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [March 1, 2012, 4:11pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/38 "2012-03-01T16:11:04Z")
> [@Bricker](#): > > Do you mean often, as in frequently? No, never. Well, hardly ever. ---
**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\ **Post date:** [March 1, 2012, 4:27pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/39 "2012-03-01T16:27:05Z")
```auto if((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) return 1; /* leap */ else return 0; /* no leap */ ``` ---
**Author:** ![Bricker](https://avatars.discourse-cdn.com/v4/letter/b/977dab/32.png) [@Bricker](https://boards.straightdope.com/u/Bricker)\ **Post date:** [March 1, 2012, 4:27pm UTC](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370/40 "2012-03-01T16:27:42Z")
> [@Musicat](#): > > No, never. Well, hardly ever. Thanks, Buttercup. [Previous page](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370.md?page=1) [Next page](https://boards.straightdope.com/t/is-2-29-an-invalid-birth-date/614370.md?page=3)