For regions like the US with a mm/dd/yy calendar order today gives 3/14/15 -- the first five digits of Pi 3.1415. going a bit further you get the first ten digits - 3.141592653 - at 9:26:53.

Only one day every century has this relation. And that brings up a curious relation with Einstein whose birthday is today. In 1915 he published his paper on General Relativity. To call it remarkable is understatement of the grandest order.

There is a foundational paper published a bit earlier with an astonishing opening paragraph. A non-technical phrasing might be: “Here is my theory of the dynamics of space and time, with an introduction to its mathematical underpinnings, as well as derivations of all the previous laws of physics within this new framework.” He mentions Grossman, but that was help with the math rather than the underlying physics. I doubt we’ll ever see such a dramatic leap penned by an individual for a theory that holds up to experiment. And it has held solidly for a century!

What you need to do is celebrate. He had a sweet tooth and liked vanilla ice cream cones with chocolate sprinkles. He also had a fondness for fruit, particularly cherry, pie - so perhaps a slice of cherry pie with a scoop of ice cream is appropriate. You might throw care to the wind and add some chocolate shavings or sprinkles...

And it is a day to celebrate William Jones - the person who believed (but didn't prove) the ratio of the circumference to the diameter of a circle was irrational and should have it's own symbol.

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the symbol for this ratio known today as π (pi) dates from the early 18th century. Before this the ratio had been awkwardly referred to in medieval Latin as: *quantitas in quam cum multiflicetur diameter, proveniet circumferencia* (the quantity which, when the diameter is multiplied by it, yields the circumference).

It is widely believed that the great Swiss-born mathematician Leonhard Euler (1707-83) introduced the symbol π into common use. In fact it was first used in print in its modern sense in 1706 a year before Euler's birth by a self-taught mathematics teacher William Jones (1675-1749) in his second book *Synopsis Palmariorum Matheseos*, or *A New Introduction to the Mathematics* based on his teaching notes.

Before the appearance of the symbol π, approximations such as 22/7 and 355/113 had also been used to express the ratio, which may have given the impression that it was a rational number. Though he did not prove it, Jones believed that π was an irrational number: an infinite, non-repeating sequence of digits that could never totally be expressed in numerical form. In *Synopsis* he wrote: '... the exact proportion between the diameter and the circumference can never be expressed in numbers...'. Consequently, a symbol was required to represent an ideal that can be approached but never reached. For this Jones recognised that only a pure platonic symbol would suffice.

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I have not come across any indication of Jones' dessert preferences. Then again he was Welsh. Pie in the day was likely meat filled.

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