r/HeresAFunFact • u/dunphish64 • Jul 06 '21
SOCIETY/CULTURE [HAFF] Despite only coming once every four years, February 29th is not the rarest birthday. There are actually 19 other dates on the calendar that are more rare to be born o.
https://imgur.com/4WUv3yy28
u/MySpiritAnimalIsPeas Jul 06 '21
Great chart! But I don't believe the data on Feb 29. Are you sure this is not showing the number of people born on that date divided by the expected number it would be if they were evenly distributed? In that case, the 29th could be taken into account by the denominator being 1/4 of what it is for the other days, and the date would not stand out much from the ones around it. If it isn't, there would need to be a good explanation for why so many more babies would be born on that day than you would expect.
Regarding the other unusual dates is that just down to dates where deliveries are unlikely to be induced and when C-sections are unlikely to be set? Christmas, New Year's and 4th of July are difficult days for hospitals, as there is less staff, but more emergencies, so they would probably avoid those days for procedures where they have a few days' flexibility.
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u/pedunt Jul 06 '21
I agree, the number is definitely relative to the expected value. There is no way that the same(ish) number of children born in a 4 year period have birthdays on Feb 28, Feb 29 and Mar 1.
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u/Twad Jul 06 '21
I call bullshit on 29/2 being so high.That's like 4 times as many people being born then rather than the surrounding days every single
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u/willie_caine Jul 06 '21
Did you take planned deliveries into consideration? Maybe people choose that day in particular because of its uniqueness, which skews it so drastically.
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u/Twad Jul 06 '21
Yes, I don't think that's enough to account for around a 300% increase.
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u/willie_caine Jul 06 '21
Is that based on a gut feeling or some data?
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u/Twad Jul 06 '21 edited Jul 06 '21
There isn't a reduction in the surrounding days that would account for so many planned births on the 29th. Look at Christmas day, there is an increased rate of births surrounding it for about a week either side. On the 29th it looks like a slight increase on the day either side as if people chose not to give their kid that birthday, it's a smaller effect but you would expect it to be as it happens 1 in 4 years and isn't a holiday.
The information was probably calculated as (number of births on day)/(times day occurred) or just by averaging births per day from the data (you wouldn't average against dates that didn't exist).
Checking your data against an expected result as a sanity check isn't just a gut feeling, it's analysis. It doesn't mean the data is wrong it's just being expressed in a different way than OP assumed.
Just woke up so I probably made some mistakes.
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u/the_timps Jul 07 '21
Is that based on a gut feeling or some data?
L O L.
So people questioning your bullshit need data.
But you claiming there's this giant stream of people planning their delivery data doesn't get one.You'd be lucky if 1% of people attempt to plan anything about their delivery date.
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u/Willowpuff Jul 06 '21
Just because it’s a cool fact, in my primary school there were 4 girls born on 29th Feb in my year and 2 boys 4 years below me. It’s was a school of 600 kids so... in a long winded way the stats seem kind of accurate albeit not commonly heard of.
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u/Twad Jul 06 '21
You were born on a leap year, you've selected a group of people based on that fact. In that year being born on that day isn't especially unlikely.
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u/Willowpuff Jul 06 '21
I just think it’s cool!
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u/Twad Jul 07 '21
Yeah it is pretty cool. Much better than getting birthday presents on Christmas Day too.
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u/Da904Biscuit Jul 07 '21
Yeah, but having 4 girls born on that day is unlikely when there's only 600 students in the whole school. That means an average of 150 students per class. I'm not great at stats but the odds of 4 girls being born on the same day has to be very small.
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u/the_timps Jul 07 '21
I'm not great at stats but the odds of 4 girls being born on the same day has to be very small.
You need less than 30 people for there to be a better 50/50 chance of two people sharing a birthday.
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u/Twad Jul 07 '21 edited Jul 07 '21
Yes it's unlikely and very interesting but a few people sharing any random birthday is quite common. In your year there was about a 1/366 chance of the most common birthday being on that day but for 3 out of 4 years there is a chance of zero.
Statistics involves looking at large amounts of information so that chances like that balance out and causal relationships become clearer.
What this post shows is that if it was day X would I expect more or fewer births than normal on average. So it ignores the fact that that date is less common. I think the title was added by someone else.
If we were looking at the same data but arranged to show the most common birthdays for a person to have it would look a bit different. There are many different ways to present the same data in a way suited to different uses.
Questioning this kind of thing is good but it's not always useful to compare it to real life anecdotes.
Edit: sorry thought you were the person I was replying to.
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Jul 06 '21
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u/Twad Jul 06 '21
You're saying people fuck 9 months in advance of a leap day to give almost 4 times the normal
? birth rate
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u/trubblebucket Jul 06 '21
I saw somewhere a theory that doctors want the holiday time off (see thanksgiving, christmas, new years, 4th of july), so often they will try to schedule c-sections and induce their natural patients ahead of time and that way everybody is happy. I do not know if this is true or not, but thought that was an interesting perspective.
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u/bettinafairchild Nov 07 '21
Hmmmm. Is it the doctors deciding not to deliver babies on major holidays, or is it the fetuses deciding not to be born on major holidays? Hmmmm?
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u/WebitoCrudoo Aug 29 '26
I believe that is also tied to the fact that many mothers don't want to "ruin" the holidays by going to the hospital during those days, so they wait a little longer than usual to consult for the pain or contractions. Just look at July 4th
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Jul 06 '21
What's so special about August? not a single day it dropped under 1.0
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u/paperairplanerace Jul 06 '21
People bang more when it's cold, and particularly over holiday breaks and/or big drinking holidays like new year's.
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u/Less_Sky_2059 Nov 29 '24
This is specifically per occurrence. So Dec 25, rarest birthday on the list. The average number of people born each Feb 29 is higher than the average number of people born each Dec 25
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u/Hugsarebadmmkay Jul 06 '21
I’m a leap day baby, and I have 2 cousins on my dad’s side whose birthdays are sept 11th and Jan 1st. I can’t wait to show them this graph!
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u/thebudman_420 Aug 18 '22
This also tells you when people have sex more often. Calculate the time in the womb on average into this. They got knocked up that long ago to have their birthday on that day on average.
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u/Munro_McLaren Feb 10 '24
Which makes no sense. I’m born on a leap year and I was nine days late. I wasn’t supposed to be born that day!
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u/BugalooShrimpp Jul 06 '21
Wow! Does anyone have an explanation for this? Is it something to do with mothers subconsciously putting off labour on big occasions or am I an idiot for saying that?