The Cosmic Calendar is a scale in which the 13.7 billion year lifetime of the universe is mapped onto a single year. At this scale the Big Bang took place on January 1 at midnight, and the current time is mapped to December 31 at midnight.

The concept was popularized by Carl Sagan in his book The Dragons of Eden and on his television series Cosmos as a way to conceptualize the vast amounts of time in the history of the universe.

Within the scheme of the Cosmic Calendar, an average human life of 70-80 years is equivalent to approximately 0.16 cosmic seconds!

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Notes:

The Cosmic Timeline: http://visav.phys.uvic.ca/~babul/AstroCourses/P303/BB-slide.htm