Cosmic Calendar

A graphical view of the Cosmic Calendar, featuring the months of the year, days of December, the final minute, and the final second

The Cosmic Calendar is a method to visualize the chronology of the universe, scaling its currently understood age of 13.8 billion years to a single year in order to help intuit it for pedagogical purposes in science education or popular science.

In this visualization, the Big Bang took place at the beginning of January 1 at midnight, and the current moment maps onto the end of December 31 just before midnight. At this scale, there are 437.5 years per cosmic second, 1.575 million years per cosmic hour, and 37.8 million years per cosmic day.

The concept was popularized by Carl Sagan in his 1977 book The Dragons of Eden and on his 1980 television series Cosmos. Sagan goes on to extend the comparison in terms of surface area, explaining that if the Cosmic Calendar were scaled to the size of a football field, then "all of human history would occupy an area the size of [his] hand".

A similar analogy used to visualize the geologic time scale and the history of life on Earth is the Geologic Calendar.

Cosmology

Date	Gya (billion years ago)	Event
1 Jan	13.8	Big Bang, as seen through cosmic background radiation, which would have been last emitted 14 minutes after midnight
19 Jan	13.1	Oldest known Gamma Ray Burst
26 Jan	12.85	First galaxies form
16 Mar	11	Milky Way Galaxy formed
13 May	8.8	Milky Way Galaxy disk formed
2 Sep	4.57	Formation of the Solar System
6 Sep	4.4	Oldest rocks known on Earth

Date in year calculated from formula

T(days) = 365 days * ( 1- T_Gya/13.797 )

Evolution of life on Earth

Date	Gya (billion years ago)	Event
14 Sep	4.1	First known remains of biotic life (discovered in 4.1 billion-year-old rocks in Western Australia).
21 Sep	3.8	First Life (Prokaryotes)
30 Sep	3.4	Photosynthesis
29 Oct	2.4	Oxygenation of atmosphere
9 Nov	2	Complex cells (Eukaryotes)
5 Dec	0.8	First multicellular life
7 Dec	0.67	Simple animals
14 Dec	0.55	Arthropods (ancestors of insects, arachnids)
17 Dec	0.5	Fish and Proto-amphibians
20 Dec	0.45	Land plants; Ordovician–Silurian extinction events
21 Dec	0.4	Insects and seeds
22 Dec	0.36	Amphibians; Late Devonian extinction
23 Dec	0.3	Reptiles
24 Dec	0.25	Permian–Triassic extinction event; 57% of all biological families and 83% of all genera die
25 Dec	0.23	Dinosaurs
26 Dec	0.2	Mammals; Triassic–Jurassic extinction event
27 Dec	0.15	Birds (avian dinosaurs)
28 Dec	0.13	Flowers
30 Dec, 06:24	0.065	Cretaceous–Paleogene extinction event, non-avian dinosaurs die out

Human evolution

Date / time	Mya (million years ago)	Event
30 Dec	65	Primates
31 Dec, 06:05	15	Apes
31 Dec, 14:24	12.3	Hominids
31 Dec, 22:24	2.5	Primitive humans and stone tools
31 Dec, 23:44	0.4	Domestication of fire
31 Dec, 23:52	0.2	Anatomically modern humans
31 Dec, 23:55	0.11	Beginning of most recent Glacial Period
31 Dec, 23:58	0.035	Sculpture and painting
31 Dec, 23:59:32	0.012	Agriculture

History begins

Date / time	kya (thousand years ago)	Event
31 Dec, 23:59:33	12.0	End of the last Ice Age
31 Dec, 23:59:41	8.3	Flooding of Doggerland
31 Dec, 23:59:46	6.0	Chalcolithic
31 Dec, 23:59:47	5.5	Early Bronze Age; Proto-writing; Building of Stonehenge Cursus
31 Dec, 23:59:48	5.0	First Dynasty of Egypt, Early Dynastic period in Sumer, beginning of Indus Valley civilisation
31 Dec, 23:59:49	4.5	Alphabet, Akkadian Empire, wheel
31 Dec, 23:59:51	4.0	Code of Hammurabi, Middle Kingdom of Egypt
31 Dec, 23:59:52	3.5	Late Bronze Age to early Iron Age; Minoan eruption
31 Dec, 23:59:53	3.0	Iron Age; beginning of classical antiquity
31 Dec, 23:59:54	2.5	Buddha, Mahavira, Zoroaster, Confucius, Achaemenid Empire, Qin Dynasty, Classical Greece, Ashokan Empire, Vedas Completed, Euclidean geometry, Archimedean Physics, Roman Republic
31 Dec, 23:59:55	2.0	Ptolemaic astronomy, Roman Empire, Christ, invention of numeral 0, Gupta Empire
31 Dec, 23:59:56	1.5	Muhammad, Maya civilization, Song Dynasty, rise of Byzantine Empire
31 Dec, 23:59:58	1.0	Mongol Empire, Maratha Empire, Crusades, Christopher Columbus voyages to the Americas, Renaissance in Europe, Classical music to the time of Johann Sebastian Bach
31 Dec, 23:59:59	0.5	Modern History; the last 437.5 years before present.

See also

• Geologic Calendar
• Big History – Academic discipline which examines history from the Big Bang to the present
• Detailed logarithmic timeline – Timeline of the universe, Earth, and mankind
• List of timelines
• Timeline of ancient history
• Timeline of early modern history
• Timeline of the evolutionary history of life
• Timeline of the far future – Scientific projections regarding the far future
• Timeline of human evolution
• Timeline of human prehistory
• Timelines of modern history
• Timeline of natural history
• Timeline of plant evolution – Chronological outline of major events in the development of plants
• Chronology of the universe – History and future of the universe
• Timeline of the Middle Ages – Timeline of events 5th–15th century CEPages displaying short descriptions of redirect targets
• Cosmic time – Time coordinate used in cosmology
• History of Earth – Development of planet Earth from its formation to the present day

External links

• More information on the image used for this article.
• The Cosmic Calendar in a Google Calendar format
• The Cosmic Calendar relayed in real time.