PLEN

The true scale of time

Earth’s history in one year

4.54 billion years

Imagine Earth forming on January 1. The moment you read these words is the very end of December 31. Scroll through the year month by month and see when everything else happened.

Earth is about 4.54 billion years old. The earliest known traces of Homo sapiens appear in this year on December 31 at about 11:25PM, 35 minutes before the end.

The Phanerozoic, the time of a rich fossil record, is the last 6 weeks of the year, from November 18.

Earth’s year in four numbers

Earth
4.54 billion yearsThe start of the year: January 1.
Dinosaurs
13 daysDecember 13 to December 26, without birds.
Homo sapiens
11:25PMDecember 31, 35 minutes before the end.
Writing
37 secondsEarly writing, the last seconds of the year.

Scroll through the year month by month. The slider shows where you are in Earth’s year: click or drag it to jump. Tap an event to explore its details.

Geologic timescale Eons

The colours of the slider and the strips are units of geologic time. Eons contain eras, eras contain periods, and periods contain epochs. In the last day of the year the slider shows epochs. Numerical boundaries are approximate; colours are chosen for this site.

  • Hadean4.54 billion years ago → 4.031 billion years agoShown from Earth’s formation 4.54 billion years ago; the ICS chart begins 4.567 billion years ago. End: ± 3 million years.
  • Archean4.031 billion years ago → 2.5 billion years agoBeginning: ± 3 million years.
  • Proterozoic2.5 billion years ago → 538.8 million years agoEnd: ± 0.6 million years.
  • Phanerozoic538.8 million years ago → presentBeginning: ± 0.6 million years.
Eras · Phanerozoic
  • Paleozoic538.8 million years ago → 251.902 million years ago
  • Mesozoic251.902 million years ago → 66 million years ago
  • Cenozoic66 million years ago → present

ICS 2026/06

January: Earth and the Moon form

3 events · about 386 million yearsfrom 4.54 to 4.15 billion years ago

  1. about January 1

    Hadean

    ≈4.54 bn yr ago

    The beginning of our planet's history.

  2. about January 4

    Hadean

    ≈4.5 bn yr ago

    The young Earth gains its natural satellite.

  3. about January 12

    Hadean

    ≈4.4 bn yr ago

    A tiny crystal survived almost Earth's entire history.

February: the 4-billion-year-old Acasta rocks

1 event · about 348 million yearsfrom 4.15 to 3.81 billion years ago

  1. about February 11

    Archean

    ≈4.03 bn yr ago

    Canada preserves fragments of ancient crust.

March: early traces of life

1 event · about 386 million yearsfrom 3.81 to 3.42 billion years ago

  1. about March 27

    Archean

    ≈3.48 bn yr ago

    Life leaves traces in very ancient rocks.

April: the giant S2 impact

1 event · about 373 million yearsfrom 3.42 to 3.05 billion years ago

  1. about April 13

    Archean

    ≈3.26 bn yr ago

    A catastrophe transforms the world of early microbes.

May: traces of an ancient ice age

1 event · about 386 million yearsfrom 3.05 to 2.66 billion years ago

  1. about May 12

    Archean

    ≈2.9 bn yr ago

    Ice left a record billions of years ago.

June: the Great Oxidation, oxygen changes the world

3 events · about 373 million yearsfrom 2.66 to 2.29 billion years ago

  1. about June 17

    Proterozoic

    ≈2.46 bn yr ago

    Even the length of a day used to be different.

  2. between June 18 and July 6

    Proterozoic

    2.45–2.22 bn yr ago

    Rocks record several separate episodes of ice.

  3. about June 22 → about July 16

    Proterozoic

    ≈2.4–2.1 bn yr ago

    Oxygen begins to transform the atmosphere.

July: the supercontinent Nuna

1 event · about 386 million yearsfrom 2.29 to 1.9 billion years ago

  1. about July 24 → about August 25

    Proterozoic

    ≈2–1.6 bn yr ago

    Vast landmasses come together long before Pangaea.

August: photosynthesis and cells with a nucleus

3 events · about 386 million yearsfrom 1.9 to 1.52 billion years ago

  1. about August 13

    Proterozoic

    ≈1.75 bn yr ago

    Tiny cells preserved structures that helped them use light.

  2. about August 21

    Proterozoic

    ≈1.65 bn yr ago

    Complex cells are part of the biosphere.

  3. about August 22

    Proterozoic

    ≈1.63 bn yr ago

    Some organisms already consist of connected cells.

September: the supercontinent Rodinia

2 events · about 373 million yearsfrom 1.52 to 1.14 billion years ago

  1. about September 10 → about September 18

    Proterozoic

    ≈1.4–1.3 bn yr ago

    An ancient supercontinent's crust stretches and cracks.

  2. about September 18 → about October 20

    Proterozoic

    ≈1.3–0.9 bn yr ago

    Bringing landmasses together takes hundreds of millions of years.

October: ancient algae

2 events · about 386 million yearsfrom 1.14 billion to 759 million years ago

  1. about October 8

    Proterozoic

    ≈1.05 bn yr ago

    Bangiomorpha reveals complex life more than a billion years ago.

  2. about October 12

    Proterozoic

    ≈1 bn yr ago

    Multicellular green algae already lived in the seas.

November: Snowball Earths and the Cambrian explosion

8 events · about 373 million yearsfrom 759 to 386 million years ago

  1. about November 4 → about November 9

    Proterozoic

    ≈717–659 M yr ago

    A remarkably long interval of extreme glaciation.

  2. before November 10 → about November 10

    Proterozoic

    >639–≈635 M yr ago

    Another global glaciation ends before the Ediacaran.

  3. about November 15

    Proterozoic

    ≈575 M yr ago

    Rich communities of large organisms enter the fossil record.

  4. about November 18 → about November 20

    Proterozoic / Phanerozoic

    ≈540–520 M yr ago

    Animal life diversifies rapidly on a geological timescale.

  5. about November 18

    Phanerozoic

    ≈539 M yr ago

    A formal boundary between geological periods.

  6. about November 24

    Phanerozoic

    ≈470 M yr ago

    Tiny fossils document plants on land.

  7. between November 26 and November 26

    Phanerozoic

    445–443 M yr ago

    The first of five major crises in this story.

    Big Five mass extinctions

  8. about November 30

    Phanerozoic

    ≈390 M yr ago

    Tracks from Poland record very early tetrapods.

December: Pangaea, dinosaurs and mass extinctions

13 events · about 373 million yearsfrom 386 to 12.4 million years ago

  1. about December 1

    Paleozoic

    ≈375 M yr ago

    A fish combines features of fins and limbs.

  2. about December 2

    Paleozoic

    ≈372 M yr ago

    Successive crises transform life in the seas.

    Big Five mass extinctions

  3. about December 7 → about December 15

    Paleozoic / Mesozoic

    ≈300–200 M yr ago

    Much of Earth's land forms a single supercontinent.

  4. about December 11

    Paleozoic

    ≈252 M yr ago

    A major crisis of life closes the Paleozoic.

    Big Five mass extinctions

  5. about December 13

    Mesozoic

    ≈230 M yr ago

    Widely accepted dinosaurs are present in the fossil record.

  6. about December 15

    Mesozoic

    ≈205 M yr ago

    An early mammaliaform lives alongside dinosaurs.

  7. about December 15

    Mesozoic

    ≈202 M yr ago

    A major crisis precedes the Jurassic world of dinosaurs.

    Big Five mass extinctions

  8. about December 19

    Mesozoic

    ≈150 M yr ago

    Stegosaurus lives long before Tyrannosaurus.

  9. about December 20 → about December 20

    Mesozoic

    ≈149–145 M yr ago

    Feathers and wings connect birds with dinosaurs.

  10. about December 21 → about December 24

    Mesozoic

    ≈130–90 M yr ago

    Flowers become an important part of the Cretaceous world.

  11. about December 26 → about December 26

    Mesozoic / Cenozoic

    ≈68–66 M yr ago

    Tyrannosaurus rex lives near the end of the Cretaceous.

  12. about December 26

    Cenozoic

    ≈66 M yr ago

    Non-avian dinosaurs disappear from the fossil record.

    Big Five mass extinctions

  13. about December 29

    Cenozoic

    ≈34 M yr ago

    Antarctica enters a new stage of its climate history.

December 31: when did humans appear?

20 events · One day of Earth’s year: about 12.4 million years

An hour, minute or second in Earth’s year is the precision of a model, not of science. We cannot date the origin of a species to the nearest minute.

The final 24 hours

One hour represents about 518,000 years. The genus Homo and the first tools appear in the evening.

  1. about December 31, 5:38PM

    Pliocene

    ≈3.3 M yr ago

    Stone tools predate our species.

  2. about December 31, 6:36PM

    Pliocene

    ≈2.8 M yr ago

    The fossil record of our genus reaches back millions of years.

  3. about December 31, 7:01PM

    Pleistocene

    ≈2.58 M yr ago

    The geological period we live in begins.

The final hour

Neanderthals and Homo sapiens overlapped in time. Short intervals become visible.

  1. about December 31, 11:14PM → about December 31, 11:55PM

    Pleistocene

    ≈400–40 k yr ago

    Another human lineage overlaps with our species.

  2. about December 31, 11:25PM

    Pleistocene

    ≈300 k yr ago

    Our species appears very late in Earth's history.

The final five minutes

This interval includes the end of the Last Glacial Maximum, the rise of farming and writing.

  1. about December 31, 11:57PM → about December 31, 11:58PM

    Pleistocene

    ≈26.5–19 k yr BP

    Ice sheets reach a vast extent during the last glacial cycle.

  2. about December 31, 11:58:37PM

    Pleistocene

    ≈12 k yr ago

    People gradually change how they obtain food.

  3. about December 31, 11:58:39PM

    Holocene

    ≈11.7 k yr b2k

    The current formal geological epoch begins.

  4. between December 31, 11:59:23PM and December 31, 11:59:24PM

    Holocene

    3300–3200 BCE

    Signs preserve information beyond human memory.

  5. about December 31, 11:59:58PM

    Holocene

    1712

    An atmospheric engine helps drain mines.

The final second

One second represents about 144 years. Aviation, antibiotics, spaceflight and the Web fit into this interval.

  1. December 31, 0.85 s before the end

    Holocene

    December 17 1903

    Controlled powered aeroplane flight becomes a reality.

  2. about December 31, 0.68 s before the end

    Holocene

    1928

    Fleming's observation opens a path to a new treatment.

  3. about December 31, 0.59 s before the end

    Holocene

    1941

    Researchers test the medicine in patients.

  4. about December 31, 0.57 s before the end → about December 31, 0.56 s before the end

    Holocene

    1944–1945

    The antibiotic becomes available on a much larger scale.

  5. December 31, 0.47 s before the end

    Holocene

    October 4 1957

    The first artificial satellite reaches Earth orbit.

  6. December 31, 0.39 s before the end

    Holocene

    July 20 1969

    Humans land on the Moon for the first time.

  7. December 31, 0.39 s before the end

    Holocene

    October 29 1969

    The first two characters reach Stanford Research Institute from UCLA.

  8. December 31, 0.30 s before the end

    Holocene

    January 1 1983

    Shared protocols enable networks to connect.

  9. about December 31, 0.26 s before the end

    Holocene

    March 1989

    Tim Berners-Lee proposes a system of linked documents.

  10. end of December 31

    Holocene

    2026

    Our little dot in Earth's long story.

The end of December 31. The moment you read these words.

How old is Earth, and how do you read its year?

We use 4.54 billion years for Earth’s age and a year of exactly 365 days. Historical dates use 2026 as their reference year. The calendar makes proportions visible, but does not make dating more precise. “Around December 13” still corresponds to an approximate geological age.

The earliest known evidence of life does not pinpoint the origin of the first cell. Species and major changes emerge through processes. Each event includes sources, dating limits and an explanation of what its marker represents.

The page scrolls event by event, so how long a month looks on screen depends on its number of cards, not on time. Time is measured by the slider, which is linear at every level, and by the headings with their real ages. In the last day of the year the slider zooms in, because the whole history of our species is too short for a scale of billions of years.

The scale of Earth’s year

1 day
about 12.4 million years
1 hour
about 518 thousand years
1 minute
about 8.6 thousand years
1 second
about 144 years

Three stories about the scale of time

Three stories help you read the proportions and understand what these dates actually tell us.

How recent are humans?

Homo sapiens against 4.54 billion years of Earth history. Compare the age of our species, agriculture and writing on a one-year scale.

Read the story

How to read Earth history in one year

How can 4.54 billion years fit into one year without losing their proportions? Understand Earth's calendar, timeline zooms and approximate dates.

Read the story

Dinosaurs did not all live together

Stegosaurus and Tyrannosaurus were separated by tens of millions of years. Find their places in December of Earth's model year.

Read the story

How good is your sense of time?

Ten questions about life, climate, people and technology. Every answer reveals the real dates and their place in Earth’s year.

Play the Earth year quiz

Frequently asked questions: Earth’s age, humans, dinosaurs

Earth is about 4.54 billion years old. We estimate this age from evidence including radiometric dating, with an uncertainty of about 50 million years. In Earth’s year, the planet’s formation marks the start of January 1, and today is the end of December 31.

It depends on what we call human. Our species, Homo sapiens, is known from fossils for about 300 thousand years, which in Earth’s year means from December 31 at about 11:25PM. The genus Homo is older: the earliest known remains are about 2.8 million years old (December 31, about 6:36PM). The stone tools from Lomekwi, older than our species, are about 3.3 million years old.

The earliest known traces of Homo sapiens are about 300 thousand years old. In Earth’s year that is December 31 at about 11:25PM, or 35 minutes before the end of the year. The whole history of our species is about 0.0066 percent of the planet’s history. There was no single moment of birth: a species emerges gradually, and new finds may move this boundary.

Early writing in Mesopotamia appears in the last 37 seconds of the year, and the beginnings of agriculture about 83 seconds before the end. Farming and writing therefore fit into the last two minutes of the year.

The earliest known dinosaurs are about 230 million years old (December 13). The extinction after which non-avian dinosaurs disappeared took place about 66 million years ago (December 26). Their era therefore lasts about 13 days of Earth’s year. Not all dinosaurs died out: birds survived and are dinosaurs.

We do not know the exact moment. The earliest known traces of life are about 3.48 billion years old (March 27), and preserved structures of oxygenic photosynthesis about 1.75 billion years old. Those structures show it existed then, but it began earlier: atmospheric oxygen was already rising about 2.4 billion years ago.

About 540 million to 520 million years ago, which in Earth’s year is November 18 to November 20. Earlier, about 575 million years ago (November 15), large Ediacaran organisms appear in the fossil record. The Cambrian explosion is a rapid diversification of animals on a geological timescale, not the moment animals were born.

About 4.5 billion years ago, which in Earth’s year is January 4. The leading explanation is a giant impact between the young Earth and another body. Researchers continue to investigate the timing and details of that process.

One day of Earth’s year is about 12.4 million years, an hour about 518 thousand years, a minute about 8.6 thousand years and a second about 144 years. This is a model conversion, not the precision of scientific dating.

The cosmic calendar popularised by Carl Sagan fits 13.8 billion years of the Universe’s history into one year, starting with the Big Bang on January 1. Our year covers only the 4.54 billion years of Earth’s history, so one day is about 12.4 million years (in the cosmic calendar about 37.8 million years). The same events therefore fall on different days and hours in the two calendars.

The time depends on three choices: whether the calendar covers the Universe or only Earth, which age we assume for humans, and whether we count the species Homo sapiens or the whole genus Homo. Here Earth is 4.54 billion years old and the earliest known traces of Homo sapiens about 300 thousand years, which gives December 31 at about 11:25PM. Changing any assumption moves that time by minutes or hours.

No. They are calculations within a model year of 365 days. Real ages, dating ranges and sources appear alongside them. A time of day in Earth’s year does not mean we can date the origin of a species to the nearest minute.

The entire history of Homo sapiens is about 0.0066 percent of Earth’s history. On a single scale spanning billions of years, people and modern inventions would be almost invisible. So on December 31 the slider zooms in: first to the whole day, then to the final hour, five minutes and second. Each level is linear, with its range labelled.

Earth’s history is divided into the Hadean, Archean, Proterozoic and Phanerozoic eons. The Phanerozoic, the time of a rich fossil record, is the last 6 weeks of Earth’s year (from November 18). Within it we distinguish the Paleozoic, Mesozoic and Cenozoic eras. These are different ranks: eons contain eras, eras contain periods, and periods contain epochs. The slider colours show eons, and in the last day epochs.

They were five major biodiversity crises during the Phanerozoic: the end-Ordovician, Late Devonian, end-Permian, end-Triassic and end-Cretaceous extinctions. Each has a separate marker beside its event. The Late Devonian involved several crises, not one continuous extinction.

Other dimensions of scale

Continue exploring

Earth in motionContinental driftTurn back time on a map. Explore Pangaea, Rodinia and the earlier history of land.QuizTest your sense of timeWhen did it happen if Earth's entire history lasts one year?In the newsThe end of the leap secondFrom 20 May 2027 UTC runs continuously. What changes and what the leap hour means.WaterWater in true scaleCompare oceans, drainage basins, and lakes. Estimate the scale, then check the data.