“E” Day

E-Day is an annual American holiday dedicated to the mathematical constant “e,” known as Euler’s number. Celebrated on February 7, this special day recognizes one of the most important numbers in mathematics, used in logarithmic calculations and many scientific applications.

History

The number “e” was first discussed about three centuries ago. Early references to this mathematical constant appeared in the work of Scottish mathematician John Napier, who described a special numerical sequence but never assigned a name to the value. He noted its importance in solving logarithmic expressions.

In 1683, Jacob Bernoulli identified the constant while working on compound interest problems, although he used the letter “b” for its notation. In 1731, Swiss mathematician Leonhard Euler studied the sequence in detail and assigned the letter “e” to the constant, taking the first letter of his last name.

Even today, the number “e” remains a source of fascination, and mathematicians continue to explore new properties and applications for this irrational and transcendental number.

Interesting Facts

• In 2018, mathematicians noticed a playful coincidence: if you read the digits of e (2.718281828) as 2/71/82/81/82/8, it loosely resembles various date formats. There’s even a connection to October 2, 1971, the start date for e-mail, a service that uses the letter “e” in its name.
• Euler’s number is often compared to Pi (π = 3.14…), another famous infinite and irrational number in mathematics.

How to Take Part

On E-Day, try solving logarithmic equations using the number “e,” or read about its discovery and significance in mathematics. Share interesting facts about Euler’s number with friends and family.

Spread the word about the holiday on social media. Ask others if they’ve ever used the number “e” in their studies or daily lives.

When Is E-Day in 2026?

E-Day is observed on February 7 every year.

Observations