Today, February 7th, 2018, is called e-day because e is approximately 2.718, and this date is written 2/7/18 in some parts of the world.
e, also called Euler’s Number after the Swiss mathematician Leonhard Euler, is a very important constant that comes up in many different places in mathematics. The numer e was discovered by the Swiss mathematician Jacob Bernoulli while studying compound interest where e arises as the limit of (1 + 1/n)n as n approaches infinity. e can also be calculated by summing:
The constant e appears naturally on the exponential function, which models growth. Hence, the same way that the constant π appears in everything that is round, the number e appears in everything that grows: size of baby animals, leaves in trees, bacteria populations, spreading of diseases, spirals in flowers and snails, radiactive decay of elements, money invested in a bank, processing power of computers… Everything that grows the faster the bigger it is follows an exponential law, and contains the number e.