e day is an annual celebration observed on February 7, 2023. The day celebrates the mathematical constant e (2.71828183) that represents the base of the natural logarithm.

Countless natural phenomena pertaining to physics, biology, and chemistry can be related to logarithmic or exponential growth. Population growth in biology, the relationship of concentrations in solution in chemistry, normal distribution equations in statistics, and compounded interest formulas in finance are only some of the real-world applications of exponential and logarithmic growth. The act of halving and doubling in nature is simply inescapable and is described by the number e and its counterpart, the natural log (ln). Numerically, e is approximately 2.718828… Similar to π, the number stretches to infinity. However, e does not receive nearly as much attention. I have yet to identify someone who passionately celebrates e-day, or see any e-day discounts. Besides, why pay 3.14 when you can pay 2.71? 

The story of e goes back to the 15th century and revolves around the work of three famous mathematicians: John Napier, Jacob Bernoulli, and Leonard Euler. Napier is credited with inventing logarithms as a method to simplify calculations involving large numbers. His invention, published in 1614 in a book called “Mirifici Logarithmorum Canonis Descriptio,” revolutionized mathematics and science and made complex calculations much easier and quicker. 

Seventy years later, Jacob Bernoulli came across the constant e while solving equations using compound interest. He noticed that as the number of compounding periods increased the equation would approach a limit. 

Eventually, Euler expanded on Napier and Bernoulis’s work and proved that the number e was irrational by proving it to be an infinite series of factorials. Ultimately, Euler’s work helped establish e as a mathematical constant with many services.

While e-day is not traceable to a specific mathematical enthusiast and is less established than π-day, e ultimately has a prominent role in the world around us. Now how do you celebrate? Maybe invest some money into a saving account, memorize a few digits of e, or try some exponential bingo!