Hadean(start: 4.6 billion years ago)The first eon, from about 4.6 billion to 4 billion years ago. The ICS chart gives 4,567 to 4,031 million years.
Archean(start: 4 billion years ago)The second eon, from about 4 billion to 2.5 billion years ago.
Proterozoic(start: 2.5 billion years ago)The third eon, from 2.5 billion to 539 million years ago. With the two eons before it, it makes up the Precambrian, an informal name.
Phanerozoic(start: 539 million years ago)The eon we live in: the last 539 million years. It is divided into three eras.
Paleozoic(start: 539 million years ago)The Phanerozoic's first era, from 539 to 252 million years ago. It has six periods.
Mesozoic(start: 252 million years ago)The middle era, from 252 to 66 million years ago. It has three periods.
Cenozoic(start: 66 million years ago)The newest era: the last 66 million years. It has three periods and seven epochs.
Periods 12
Cambrian(start: 539 million years ago)The Paleozoic's first period, from 539 to 487 million years ago. The USGS chart of 2018 gives 541 for its start.
Ordovician(start: 487 million years ago)The Paleozoic's second period, from 487 to 443 million years ago. The USGS chart of 2018 gives 485 for its start.
Silurian(start: 443 million years ago)The Paleozoic's third period, from 443 to 420 million years ago. The USGS chart of 2018 gives 444 for its start.
Devonian(start: 420 million years ago)The Paleozoic's fourth period, from 420 to 359 million years ago. The USGS chart of 2018 gives 419 for its start.
Carboniferous(start: 359 million years ago)The Paleozoic's fifth period, from 359 to 299 million years ago. The USGS chart divides it into the Mississippian and the Pennsylvanian.
Permian(start: 299 million years ago)The Paleozoic's last period, from 299 to 252 million years ago.
Triassic(start: 252 million years ago)The Mesozoic's first period, from 252 to 201 million years ago.
Jurassic(start: 201 million years ago)The Mesozoic's middle period, from 201 to 143 million years ago.
Cretaceous(start: 143 million years ago)The Mesozoic's last period, from 143 to 66 million years ago. The USGS chart of 2018 gives about 145 for its start.
Paleogene(start: 66 million years ago)The Cenozoic's first period, from 66 to 23 million years ago. Older charts join it with the next period as the Tertiary, a name the USGS still recognizes.
Neogene(start: 23 million years ago)The Cenozoic's second period, from 23 million to 2.58 million years ago.
Quaternary(start: 2.58 million years ago)The period we live in: the last 2.58 million years.
Epochs 7
Paleocene(start: 66 million years ago)The Paleogene's first epoch, from 66 to 56 million years ago.
Eocene(start: 56 million years ago)The Paleogene's second epoch, from 56 to 34 million years ago.
Oligocene(start: 34 million years ago)The Paleogene's last epoch, from 34 to 23 million years ago. The ICS chart gives 33.9 for its start.
Miocene(start: 23 million years ago)The Neogene's first epoch, from 23 million to 5.3 million years ago.
Pliocene(start: 5.3 million years ago)The Neogene's second epoch, from 5.3 million to 2.58 million years ago.
Pleistocene(start: 2.58 million years ago)The Quaternary's first epoch, from 2.58 million to 11,700 years ago.
Holocene(start: 11,700 years ago)The epoch we live in: the last 11,700 years.
How this list was compiled: Names, ranks, order and ages checked on 2026-09-30 in two places. (1) The International Commission on Stratigraphy, International Chronostratigraphic Chart, version 2026-06, https://stratigraphy.org/chart (the chart's own data, read from the page). (2) The U.S. Geological Survey Geologic Names Committee, Divisions of Geologic Time: Major Chronostratigraphic and Geochronologic Units, Fact Sheet 2018-3054, https://pubs.usgs.gov/fs/2018/3054/fs20183054.pdf, which also gives the Mississippian and Pennsylvanian, the Tertiary, the informal Precambrian and the standing of the Anthropocene. Licence: own work
The drawing: Drawn for this site on 2026-09-30. Own original chart; the order of the divisions follows the ICS and USGS charts, and nothing is traced or copied. Licence: own work
How it works
These geologic time scale worksheets share one chart of 26 boxes: the eons and eras, the twelve periods and the seven newest epochs. Print it blank, numbered or filled in, then quiz yourself on the names and the dates.
Read the full guide
How to read the chart
Every row runs from the oldest box at the left, and the chart ends at today. An eon is the longest division; eras divide an eon, periods an era and epochs a period. The boxes are all one size: the chart shows the order, not how long each division lasted.
A geological time scale worksheet with dates
Blank leaves the boxes empty to write in, Numbered adds a line for each name and Named is the key. The quiz asks each name and then when that division began. Ages follow the International Chronostratigraphic Chart of June 2026, rounded; where the USGS chart of 2018 differs, a typed answer may use either figure.
Learn the three eras first; every period and every epoch belongs to one of them.
USGS charts split the Carboniferous into two: the Mississippian, then the Pennsylvanian.
Questions and answers
What are the divisions of the geologic time scale?
From longest to shortest: eons, eras, periods and epochs. The four eons are the Hadean, Archean, Proterozoic and Phanerozoic. The Phanerozoic has three eras: the Paleozoic, the Mesozoic and the Cenozoic.
What are the 12 periods in order?
Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian in the Paleozoic; Triassic, Jurassic and Cretaceous in the Mesozoic; Paleogene, Neogene and Quaternary in the Cenozoic.
Why do some charts show the Mississippian and Pennsylvanian?
They are the two parts of the Carboniferous. The Mississippian is the older and the Pennsylvanian the younger; the line between them is about 323 million years ago. The USGS chart shows both names.
What is the Precambrian?
An informal name for the time before the Cambrian: the Hadean, Archean and Proterozoic eons together, from about 4.6 billion to 539 million years ago. It has no rank of its own.
What epoch do we live in?
The Holocene, which began 11,700 years ago. It is the latest epoch of the Quaternary period, in the Cenozoic era of the Phanerozoic eon. The Anthropocene is not a formal division on the chart.