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π Happy International Pi Day! (the 314th day of the year)
🥧 This morning I celebrated with an apple hand pie, purchased from the newest Tartine Bakery in Mill Valley (https://tartinebakery.com/san-francisco/mill-valley) last Saturday. Through trial and error I learned that Reheat at 325F (default) for 4 minutes worked best to heat the filling enough to be very warm, but not hot enough to burn your mouth (settings for a Breville mini oven / “air fryer”).
After several years of celebrating today as “ordinal pi day”, derived from the “ordinal date” standardized by ISO 8601 (https://en.wikipedia.org/wiki/ISO_8601#Ordinal_dates), I decided it merited elevation to International Pi Day, since ordinal dates are an international standard, and counting days works the same worldwide.
As noted in previous years, celebrating pi day on March 14th is US-centric, because more countries (people) write their dates day/month instead of the US month/day convention (https://en.wikipedia.org/wiki/List_of_date_formats_by_country#Usage_map). March 14th is a US National Pi day at best.
It’s about time we declared the only standardized nth day of the year as our method for declaring international number-related holidays.
The list so far of such international nth day of the year holidays:
* 088: World Piano Day
* 256: 8-Bit Day (https://tantek.com/2026/256/t1)
* 314: International Pi Day (or World Pi Day if you prefer)
Previously:
* https://tantek.com/2025/314/t1/happy-ordinal-pi-day
#piDay #internationalPiDay #worldPiDay #actualPiDay #ordinalDate #ordinalDates #ISO8601 #ISOdate #standards #ordinal #pi
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π Happy ordinal pi day! (314th day of the year)
No, it should not be the US-centric March 14th, which most of the world writes as 14/3 or 14-3.
Science and mathematics are international, without borders, not specific to any one country or culture. As scientists and mathematicians we should seek international-based celebrations that bring us all together around the globe rather than country-specific dates.
The ordinal date (ISO 8601) is the only way to have an international nth day of the year: https://en.wikipedia.org/wiki/Ordinal_date
Similarly:
* 88th day: worldwide Piano Day: https://en.wikipedia.org/wiki/Piano_Day (blogged https://tantek.com/2024/088/t1/world-piano-day-ordinal-date-iso-8601)
* 256the day: 8-bit day or https://en.wikipedia.org/wiki/Programmer%27s_Day (blogged https://tantek.com/2025/257/t1/happy-8bitday-255-bytes-max)
I suspect there are other such annual worldwide holidays that are pinned to the ordinal date rather than a Gregorian or other non-decimal calendar. Let me know if you have a favorite that you celebrate!
🥧 I haven't made a pie (or picked one up) yet — will have go pick up a slice during a break in this evening’s #w3cTPAC meetings (which are in Japan where it’s already the day after pi day).
Previously:
* https://tantek.com/2022/314/t1/happy-ordinal-pi-day
#piDay #actualPiDay #ordinalDate #ISO8601 #ISOdate
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