|When is eDay?|
|What is eDay?|
eDay, like Pi Day and Mole Day, is an informal international celebration of a special number. In this case, "e" stands for Euler's constant. This irrational number, named after Swiss mathematician Leonhard Euler, is used in logarithmic scales and other expressions of exponential growth as a way to indicate the concept that a continually growing system scales at a common rate. Since "e" is an irrational number, it has an infinite number of decimal places. It is typically rounded to 2.71828. In countries that use the month/day format for marking dates, the celebration falls on the seventh of February (2/7). For nations that use day/month, the date is the 27th of January (27/1).
Other celebrations around the world are also designated as "e-day" including New Zealand's electronic waste disposal day. Engineer's Day and Euro Day are also sometimes called e-day.