Cosmic Calendar

The Cosmic Calendar is a method to visualize the chronology of the universe, scaling its currently understood age of 13.787 billion years to a single year in order to help intuit it for pedagogical purposes in science education or popular science. A similar analogy used to visualize the geologic time scale and the history of life on Earth is the Geologic Calendar.

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

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.^[1] At this scale, there are 438 years per cosmic second, 1.58 million years per cosmic hour, and 37.8 million years per cosmic day.

The Solar System materialized in Cosmic September. The Phanerozoic corresponds only to the latter half of December, with the Cenozoic only happening on the penultimate day on the Calendar. The Quaternary only applies to the last four hours on the final Cosmic Day, with the Holocene only applying to the final 23 Cosmic Seconds. On the other hand, relic radiation is dated at the first fifteen minutes of the very first Cosmic Day; even if we stretch the Cosmic Calendar to 100 years, the relic radiation would still happen just after the start of the second Cosmic Day.

The concept was popularized by Carl Sagan in his 1977 book The Dragons of Eden and on his 1980 television series Cosmos.^[2] 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".^[3] The Cosmic Calendar was reused in the 2014 series, Cosmos: A Spacetime Odyssey.^[4]

Cosmology

Sources^[5][6]

Date	Gya (billion years ago)	Event
1 January, 0:00	13.787	The Big Bang[7]
1 January, 0:14	13.787	The cosmic background radiation. Would have been last emitted 14 minutes after midnight
1 January, 0:30	13.787	First atoms
19 January	13	GRB 090423, Oldest known Gamma Ray Burst
26 January	12.85	First galaxies form[8]
1 March	11	Milky Way Galaxy formed
13 May	8.8	Milky Way Galaxy disk formed
9 September	4.57	Formation of the Solar System
14 September	4.5	Formation of the Earth and The Moon

Date in year calculated from formula

T(days) = 365 days * ( 1- T_Gya/13.787)

Evolution of life on Earth

Date	Gya (billion years ago)	Event
14 September	4.1	First known remains of biotic life (discovered in 4.1 billion-year-old rocks in Western Australia).[9][10]
21 September	3.8	First Life (Prokaryotes)[11][12][13]
30 September	3.4	Photosynthesis
29 October	2.4	Oxygenation of atmosphere
9 November	2	Complex cells (Eukaryotes)
5 December	0.8	First multicellular life[14]
7 December	0.67	Simple animals
14 December	0.55	Arthropods (ancestors of insects, arachnids)
17 December	0.53	Fish and Proto-amphibians
18 December	0.518	Vertebrates
19 December	0.45	Land plants; Ordovician–Silurian extinction events
20 December	0.4	Jawed fish
21 December	0.35	Insects and seeds
22 December	0.33	Amphibians; Late Devonian extinction
23 December	0.3	Reptiles
24 December	0.25	Permian–Triassic extinction event; 57% of all biological families and 83% of all genera die
25 December	0.23	Dinosaurs
26 December	0.201	Mammals; Triassic–Jurassic extinction event
27 December	0.072	Birds (avian dinosaurs)
28 December	0.13	Flowers
30 December, 6:24	0.066	Cretaceous–Paleogene extinction event, non-avian dinosaurs go extinct;[15] Primates

Human evolution

Date / time	Mya (million years ago)	Event
31 December, 6:05	28	Apes
31 December, 14:24	12.3	Hominids
31 December, 20:00	7	Chimpanzees and Humans split
31 December, 22:24	2.8	Homos and stone tools
31 December, 23:44	0.4	Domestication of fire
31 December, 23:52	0.2	Humans
31 December, 23:55	0.115	Beginning of most recent Glacial Period
31 December, 23:58	0.035	Sculpture and painting
31 December, 23:59:32	0.012	Agriculture

History begins

Date / time	kya (thousand years ago)	Event
31 December, 23:59:33	11.7	End of the last Ice Age
31 December, 23:59:41	8.3	Flooding of Doggerland
31 December, 23:59:46	6	Chalcolithic
31 December, 23:59:47	5.5	Early Bronze Age; Proto-writing; Building of Stonehenge Cursus
31 December, 23:59:48	5	First Dynasty of Egypt, Early Dynastic period in Sumer, beginning of Indus Valley civilisation
31 December, 23:59:49	4.5	Alphabet, Akkad, wheel
31 December, 23:59:51	4	Code of Hammurabi, Middle Kingdom of Egypt
31 December, 23:59:52	3.5	Late Bronze Age to early Iron Age; Minoan eruption
31 December, 23:59:53	3	Iron Age; beginning of classical antiquity
31 December, 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 December, 23:59:55	2	Ptolemaic astronomy, Roman Empire, Jesus, invention of numeral 0, Gupta Empire
31 December, 23:59:56	1.5	Muhammad, Maya civilization, Song dynasty, Black Death, Byzantine Empire
31 December, 23:59:58	1	Mongol Empire, Maratha Empire, Crusades, Christopher Columbus voyages to the Americas, Renaissance in Europe, Classical music to the time of Johann Sebastian Bach
31 December, 23:59:59	0.5	Modern History; the last 437.5 years before present. 7 Years War, American and French Revolutions, Airplanes, World War 1 and 2, Computers, Spaceflight, First human landing on The Moon