The Cosmic Calendar is a concept introduced by astronomer Carl Sagan in his television series "Cosmos: A Personal Voyage." It is a way of conceptualizing the history of the universe in relation to a calendar year, with the Big Bang occurring on January 1st and the present day falling at the end of December 31st. Each month represents approximately 1.33 billion years, and each day represents around 40 million years. This visualization helps to illustrate the vast timeline of the universe and the relatively recent appearance of humans on Earth.
