Carl Sagan's Cosmic Calendar

The American astronomer Carl Sagan was the first to suggested a “cosmic calendar”. He put everything starting from Big Bang to till today into a scale of a calendar year. According to Carl Sagan the Big Bang corresponding to the first second of the New Year's Day, and the present time to the last second of December 31st (midnight). Using this scale of time, each month would equal a little over a billion years.

Within the scheme of the Cosmic Calendar, an average human life of 70-80 years is equivalent to approximately 0.16 cosmic seconds. All human history is crowded into last 5 minutes of the last day of the year. Recent time has to be divided into seconds and fraction of seconds. So everything happened over the last 475 years take place in less than the last second of the last minute of the year.

Date/Time	Event
1 Jan(midnight)	Big Bang
15 Mar	First star and galaxies form
1 May	Milky Way galaxy form
8 Sep	Sun forms
9 Sep	Solar System forms.
12 Sep	Earth forms.
13 Sep	Moon forms.
20 Sep	Earth’s atmosphere forms.
1 Oct	Earliest known life on earth.
7 Oct	Earliest Known fossils.
18 Dec	First many celled life forms.
19 Dec	First Fish.
21 Dec	First land plants
23 Dec	First reptiles.
24 Dec	First Dinosaurs.
26 Dec	First mammals.
27 Dec	First birds.
28 Dec	Dinosaurs extinct.
31 Dec	Homo sapiens (modern human) appears.