The cosmic calendar is a way of visualizing natural history by compressing the entire history of the universe into a single year. In this calendar, the Big Bang occurred at midnight on January 1, and the present time is the last milliseconds of December 31. The Milky Way galaxy was formed in mid-May, and our solar system in September. Multicellular life appeared in early December, the first vertibrates on December 22, dinosaurs on Christmas Day, humans in the late night hours of New Year's Eve.