International Day of Mathematics

Every year on March 14th, mathematicians celebrate the International Day of Mathematics, also known as Pi Day.

Why March 14th?

March 14th was solemnly celebrated as Pi Day by math-enthusiasts around the world before the International Day of Mathematics came into being. The well-known circle constant Pi, which specifies the ratio of the circumference of a circle to its diameter, has an infinite amount of digits but is commonly known as 3.14. In some countries, March 14th is written as 3/14 (so almost 3.14). For math-enthusiasts, this was enough of a reason to celebrate and for the International Mathematical Union, it was reason enough to pick up the date and declare this day the annual International Day of Mathematics.

30 trillion digits and nowhere near the end

In Ancient Egypt mathematicians already knew that Pi was the ratio of the circumference of a circle to its diameter. At first, however, the quantification of Pi was not very precise. Determining the digits by hand using geometric or numerical methods was and still is a great challenge, and errors kept happening throughout history. It took several hundred years to determine the first 707 digits, only to find out about 70 years later that not all 707 digits were correct.

The big breakthrough in determining Pi came with the help of computers in the second half of the 20th century. The number of known digits rose rapidly from a few hundred to a few trillion in the early 21st century. Of course, there is still no end in sight.

The fact that we use the Greek letter π today is largely due to the Basel mathematician Leonhard Euler. The first documented use of π is not attributable to him, but it was Euler who popularized its use.

π = 3.141592…6335[4 15 07]46088...

In addition to Pi's undisputed place in mathematical research, more and more curiosities, entertaining facts, and applications spawned over the years. For example, it is possible to find any date of birth in the tangle of Pi's digits. Leonhard Euler's birthday, for example, is at position 20.625 in Pi's digits (4/15/1707 π = 3.141592…6335 [4 15 07]46088...). If you want to determine your own Pi day, you can either search the infinite digits of Pi by yourself or use one of the many Pi birthday calculators available on the internet.

Events and information

In the course of the International Day of Mathematics, various institutions hold exciting events and lectures every year. Here  you can find an overview of some events.

Further information can also be found on the website of the International Mathematical Union and the Pi Day website.