Cosmic Calendar

The whole history of the universe squeezed into one year. Find where any moment falls.

Your answer

Where your moment falls in the year of the universe

Enter how long ago something happened, a year in history or the year you were born, and this space places it on the calendar, between the events either side of it, with a gold hand on the dial.

The calendar

The year of the universe, month by month

Eight months pass with no Sun at all. Earth arrives in early September, the first animals big enough to see in mid-December, and every one of the events in red happens on the last day.

January

13.8 billion years to 12.6 billion years ago

1 January: The Big Bang
6 January: First stars
8 January: Earliest galaxies seen
22 January: The Milky Way's oldest stars

February to August

12.6 billion years to 4.61 billion years ago

Galaxies gather and stars live and die, making the carbon, oxygen and iron that later build planets.

September

4.61 billion years to 3.48 billion years ago

2 September: The Sun is born
2 September: Earth forms
3 September: The Moon forms
6 September: First oceans
25 September: First signs of life
30 September: Oldest fossils of microbes

October

3.48 billion years to 2.31 billion years ago

29 October: Oxygen fills the air

November

2.31 billion years to 1.17 billion years ago

14 November: Complex cells

December

1.17 billion years to 0 years ago

4 December: Oldest known sex
16 December: First large animals
17 December: Cambrian explosion
19 December: Plants reach land
21 December: First forests
22 December: Fish walk onto land
25 December: The Great Dying
25 December: First dinosaurs
26 December: First mammals
28 December: First birds
28 December: First flowers
30 December: The dinosaurs end
31 December: Our line splits from chimpanzees
31 December: First stone tools
31 December: Fire
31 December: Homo sapiens
31 December: People reach Australia
31 December: Farming begins
31 December: Writing
31 December: The Great Pyramid
31 December: The Roman Empire at its largest
31 December: Copernicus puts the Sun at the centre
31 December: Galileo turns a telescope to the sky
31 December: Newton's laws of motion and gravity
31 December: Einstein's general relativity
31 December: People walk on the Moon
31 December: The World Wide Web opens

31 December

The last day, by the clock

Everything written down by anyone fits in the final 12 seconds.

19:52:26Our line splits from chimpanzees, 6.5 million years ago
Estimated from fossils and DNA at 6 to 7 million years.
21:54:18First stone tools, 3.3 million years ago
Found at Lomekwi in Kenya, older than our own genus.
23:21:54Fire, 1 million years ago
Ash and burnt bone in Wonderwerk Cave, South Africa: the oldest firm evidence.
23:48:34Homo sapiens, 300,000 years ago
The oldest fossils of our species, from Jebel Irhoud in Morocco.
23:57:31People reach Australia, 65,000 years ago
Madjedbebe in Arnhem Land is dated to about 65,000 years; some argue for 50,000.
23:59:32.5Farming begins, 12,025 years ago
Wheat and barley are first grown in the Fertile Crescent.
23:59:48.1Writing, 5,225 years ago
Cuneiform in Mesopotamia and hieroglyphs in Egypt.
23:59:49.5The Great Pyramid, 4,585 years ago
Built for the pharaoh Khufu at Giza.
23:59:55.6The Roman Empire at its largest, 1,909 years ago
Under the emperor Trajan.
23:59:58.9Copernicus puts the Sun at the centre, 483 years ago
His book is published the year he dies.
23:59:59.047Galileo turns a telescope to the sky, 417 years ago
He soon sees the moons of Jupiter and the phases of Venus.
23:59:59.225Newton's laws of motion and gravity, 339 years ago
Principia explains the planets and the falling apple with one law.
23:59:59.746Einstein's general relativity, 111 years ago
Gravity becomes the bending of space and time.
23:59:59.870People walk on the Moon, 57 years ago
Apollo 11 lands on 20 July.
23:59:59.920The World Wide Web opens, 35 years ago
The first website goes live at CERN.

The scale

How much time each part of the calendar holds

On the calendar	In real time
1 month	about 1.15 billion years
1 day	about 37.8 million years
1 hour	about 1.58 million years
1 minute	about 26,300 years
1 second	about 438 years

The working

Take how long ago something happened and divide by the age of the universe, 13.8 billion years. Subtract that from 1 to get how far through the year it falls, then multiply by the 31,536,000 seconds in a 365-day year. The dinosaurs ended 66 million years ago: 66 ÷ 13,800 = 0.00478, so 1 − 0.00478 = 0.99522 of the way through, which is 31,385,176 seconds into the year: 30 December at 06:06.

Print room

The whole calendar on one sheet

Every event with its cosmic date, time and real age, for a classroom wall or a fridge door.

The Cosmic Calendar: 13.8 billion years as one year

Cosmic date and time	Event	Real time ago
1 January, 00:00:00	The Big Bang	13.8 billion years
6 January, 06:57:23	First stars	13.6 billion years
8 January, 22:26:05	Earliest galaxies seen	13.5 billion years
22 January, 03:49:33	The Milky Way's oldest stars	13 billion years
2 September, 03:02:36	The Sun is born	4.57 billion years
2 September, 22:05:13	Earth forms	4.54 billion years
3 September, 23:28:41	The Moon forms	4.5 billion years
6 September, 14:57:23	First oceans	4.4 billion years
25 September, 03:18:15	First signs of life	3.7 billion years
30 September, 22:57:23	Oldest fossils of microbes	3.48 billion years
29 October, 12:31:18	Oxygen fills the air	2.4 billion years
14 November, 09:23:28	Complex cells	1.8 billion years
4 December, 05:28:41	Oldest known sex	1.05 billion years
16 December, 19:00:00	First large animals	575 million years
17 December, 17:58:44	Cambrian explosion	539 million years
19 December, 13:39:07	Plants reach land	470 million years
21 December, 19:36:31	First forests	385 million years
22 December, 01:57:23	Fish walk onto land	375 million years
25 December, 08:02:05	The Great Dying	252 million years
25 December, 22:00:00	First dinosaurs	230 million years
26 December, 17:02:36	First mammals	200 million years
28 December, 00:46:57	First birds	150 million years
28 December, 13:28:41	First flowers	130 million years
30 December, 06:06:15	The dinosaurs end	66 million years
31 December, 19:52:26	Our line splits from chimpanzees	6.5 million years
31 December, 21:54:18	First stone tools	3.3 million years
31 December, 23:21:54	Fire	1 million years
31 December, 23:48:34	Homo sapiens	300,000 years
31 December, 23:57:31	People reach Australia	65,000 years
31 December, 23:59:32.5	Farming begins	12,025 years
31 December, 23:59:48.1	Writing	5,225 years
31 December, 23:59:49.5	The Great Pyramid	4,585 years
31 December, 23:59:55.6	The Roman Empire at its largest	1,909 years
31 December, 23:59:58.9	Copernicus puts the Sun at the centre	483 years
31 December, 23:59:59.047	Galileo turns a telescope to the sky	417 years
31 December, 23:59:59.225	Newton's laws of motion and gravity	339 years
31 December, 23:59:59.746	Einstein's general relativity	111 years
31 December, 23:59:59.870	People walk on the Moon	57 years
31 December, 23:59:59.920	The World Wide Web opens	35 years

1 cosmic second ≈ 438 years · calculationtime.com/calendars/cosmic-calendar/

Questions

Questions people ask about the Cosmic Calendar

Who came up with the Cosmic Calendar?

The astronomer Carl Sagan, in his 1977 book The Dragons of Eden, and later on screen in Cosmos. He used it to show how late people arrive in the story.

How long is one second on the Cosmic Calendar?

About 438 real years. A minute is about 26,000 years, an hour about 1.6 million, a day about 38 million and a month a little over a billion.

When do people appear?

Our species, about 300,000 years old, arrives at about 23:48 on 31 December. Everything written down, from the first cuneiform tablets to today, fits in the last 12 seconds.

Why is the universe 13.8 billion years old here?

That is the age measured from the afterglow of the Big Bang by the Planck satellite: 13.787 billion years, give or take 20 million. Rounding it moves the dates by well under a day.

Are the dates exact?

The clock arithmetic is exact; the events are not. Many are estimates with wide margins, such as the first life or the first complex cells, and each note says where scientists still disagree.

What happens to the calendar as time goes on?

Each real year adds about two thousandths of a cosmic second, so the calendar barely moves in a lifetime. Recent events do drift back from midnight: the Moon landing sits a little further from it every year.

Sources

Where the ages come from

The age of the universe is rounded to 13.8 billion years. Ages of rocks and fossils follow the stratigraphy chart and the papers named in each note; recent history uses calendar years, so those ages count up each year.