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# e Day – Euler's constant

E-Day celebrates the mathematical constant “e” (2.7182818) on February 7 (2/7) in the month/day date format or January 27 (27/1) in the day/month format.

## What is e?

Euler’s constant “e” is also known as “Euler’s number” after the Swiss mathematician Leonhard Euler. The constant e was discovered by several mathematicians who didn’t know of its significance until Euler started to use the letter e for the constant around 1727. It is an irrational number that represents the idea that all continually growing systems are a scaled version of a common rate. The constant e is mostly used in logarithms, exponential growth, and complex numbers.

### More special calendar dates!

The letter e in e-Day is also used to represent other events and words that begin with the letter e.

## What do people do?

Many celebrate e-Day as Euler’s constant day on February 7 (2/7) in the month/day date format. It is a day where people recognize the significance of the number e, which is approximately 2.71828. Although this is the most commonly recognized holiday for e-Day, there are other worldwide events that are observed that have nothing to do with the e number constant.

Euro day occurred in European countries that simultaneously adopted the Euro on January 1, 2002. In New Zealand, eDay is a day where people can get rid of e-waste or old electronics such as computers and old appliances, so they can be recycled rather than being placed in a landfill. Engineer’s Day is observed in Paducah, Kentucky on February 21 where many have an egg drop contest, create edible cars and tape people to walls. Eday is also an island in Northern Scotland.

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