Put another spritz of pneapple juice in the pna colada and pass the pzza. Today is Pi Day.

People who follow this column — I know your names and I know where you both live — may have wondered why it wasn’t published on its usual day, Monday. I saved it for today, because — drum roll, please — the date is 3/14!

Ah, did a mental lightbulb just click on?

Pi, as your middle-school math teacher tried to pound into your head, is the near-mystical (and emphatically irrational, as well as transcendental) number that relates the distance around a circle to its diameter. In math formulas, it’s written as p.

Millions of schoolchildren

have made near-endless calculations from the general equations for circumference (C=2pr) and the area of a circle (A=pr2 ). For many people, that may have been their last encounter with p, unless they went into careers as

scientists, engineers, toolmakers or designers. But p shows up in many strange places, including the DNA double helix, the equations describing rainbows in the sky and ripples on a pond, celestial navigation and the Egyptian and Mayan pyramids.

People usually approximate the value of pi, often to about five digits such as 3.1416. Supercomputers have added 1.2 trillion digits to the right of the decimal place and still not found either an end point or a repeating pattern.

Some people have tried to oversimplify p. I remember reading in Robert A. Heinlein’s “Stranger in a Strange Land” a passing reference to the Tennessee legislature’s attempt to officially round off p to 3.14. Heinlein had it wrong. Other writers also have incorrectly blamed or credited Alabama, Oklahoma, Kentucky and Kansas with “trying to legislate the value of pi.” The mathematically-challenged lawmakers in fact were members of the Indiana House of Representatives, who somehow convinced themselves (unanimously) in 1897 that they could both patent new values for p and earn royalties by licensing the use of said values. The curiously named, but very much real-life mathematician Professor C.A. Waldo convinced the Indiana Senate to table the bill and, at last report, it remains in legislative limbo.

Nothing about p is normal, which helps explain people’s abnormal fascination with it since the days of ancient Babylonia. Pi can’t be expressed as a fraction, although 22/7 and 355/13 come close, so by mathematicians’ definition p is “irrational.” They also say it is “trancendental,” a concept I’m not prepared to explain. I think it suffices to say that p to the 40th decimal place will accurately inscribe a near-perfect circle (within a photon’s width) around the visible universe — which brings me as transcendentally close to infinity as I expect to be this side of Heaven.

Speaking of 22/7, some people (primarily Europeans, who use a different calendar notation) observe July 22 as Pi Approximation Day.

I say they’re far off the mark.

I became aware of Pi Day some years ago while serving as president of a children’s science center modeled on the famous Exploratorium in San Francisco. The Exploratorium started its annual Pi Day celebration in 1989. I doubt that was the first Pi Day, but it set the standards for many to follow.

Pi Day activities traditionally start on March 14 at 1:59 p.m.. (3-1-4-1-5-9) when guests form a circle and rotate it 3.14 times.

They toast p (and also the memory of Albert Einstein, born on March 14, 1879) with pineapple juice or pina coladas and snack on “Newton’s” apple pie, pie a la Mode (served first to the largest group of guests with the same age or birth month, the mathematical mode) and pizza.

Games include pie-eating contests, competitions among those who have memorized p to the finest decimal place (Akira Haraguchi of Japan set a world record in 2005: 83,431 numbers recited over about eight hours) and p trivia contests (sample answers: Mr. Spock in “Wolf In the Fold,” Arthur C. Clarke and “Childhood’s End” or “Time’s Eye” and Professor Frink in “The Simpsons”).

Pi Day partiers also string necklaces with color-coded beads, each one representing a value of 0 to 9. The longest string at the Exploratorium represents 1,600 digit of pi.

People sing songs about p and recite poetry. They listen to music, such as Kate Bush’s “p” (she sings p to its 137th decimal place, missing one number) and Hard ’n Phrim’s “Pi” (3.14 minutes long).

When someone turns out the lights, or at midnight, the party ends. Pi rounds down, not up.

It’s yet to be seen whether Pi Day, like p and love, will go on forever. But 10 years from now, wherever I’m living, come on over to my house.

The drinks will be on me on 3/14/16 ... in the future.