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Comment by Andrex | Hacker News Reader

Aren't there 366 birthdays, not 365?

Are leap-day births unpersons?

I wonder if most celebrate March 1 or February 28 most of the time? March 1 is more accurate time-wise but February 28 keeps within the same month.

Most do March 1. That comports withs the legal recognition of age.

But some will do Feb out of consistency of month.

Some cultures (not the US apparently) consider wishing an early birthday bad luck so I'd expect them never to celebrate on Feb 28. I know this is a thing in Central Europe, not sure how common it is. It was a big culture clash in a company I know when they moved HQ from Germany to the US because the Germans would get offended by Americans wishing them happy birthday when their birthdays were on the weekend or a bank holiday.

The Islamic calendar has 354 or 355 days. https://en.wikipedia.org/wiki/Islamic_calendar

File under "Falsehoods programmers believe about time."

There are approximately 365¼ days in a standard solar year.

“I will leave out extra material from the original including […] accounting for leap years”

No but they rarely have birthdays

If we're going off of rarity, December 25 has 6,574 average yearly births and September 9 has almost double at 12,301 average yearly births.

Taking a look at Feb 29th, it has 10467 average yearly births (for years that have a Feb 29th).

So what is the level of rarity that makes a day not worth calculating?

https://github.com/fivethirtyeight/data/blob/master/births/U...

> it has 10467 average yearly births (for years that have a Feb 29th)

do you see it?

To spell it out: leap years happen less than every four years, so the average birth rate over four years is actually closer to 2,616 - quite outside the range of 6,574 - 12,301.

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