List of time periods

This is a list of named time periods defined in verious fields of study.

This list is under construction: the eventual aim is for it to be a compendium of names of eras and epochs in all fields of study

To do:

• periods should have approximate dates added in the format (start - finish)
• lists should be in chronological order of the start of their period.

See periodization for a discussion of the tendency to try to fit history into non-overlapping periods.

See also List of timelines for a list of timelines in general.

Table of contents 1 Cosmological time periods 2 Geologic time periods 3 Human time periods 3.1 Calendar systems 3.2 Human prehistorical periods 3.3 Human historical periods 3.4 Specialist human periods

Cosmological time periods

The cosmological timescale is the longest imaginable. It covers the entire extent of the universe - many billions of years. A short first period is measured in tiny fractions of seconds, but thereafter most things happen on the scale of billion years. It is used to consider events noticeable on a universal scale, such as the formation of matter, stars, and galaxies.

• The Big Bang

Geologic time periods

The geologic timescale covers the extent of the existence of Earth, from about 4600 million years ago to the present day. It is used to consider the formation and change of the Earth itself, and large-scale changes in the planet's inhabitants.

Dates are given as Millions of Years Ago (MYA).

Eon	Era	Period	Epoch
Precambrian (4600-544 MYA)	Hadean (4600-3800 MYA)
	Archaean (3800-2500 MYA)
	Proterozoic (2500-544 MYA)
Phanerozoic (544 MYA - now)	Paleozoic (544-245 MYA)	Cambrian (544-505 MYA)
		Ordovician (505-440 MYA)
		Silurian (440-410 MYA)
		Devonian (410-360 MYA)
		Carboniferous (360-286 MYA)	Mississippian (360-325 MYA)
			Pennsylvanian (325-286 MYA)
		Permian (286-245 MYA)
	Mesozoic (245-65 MYA)	Triassic (245-208 MYA)
		Jurassic (208-146 MYA)
		Cretaceous (146-65 MYA)
	Cenozoic (65 MYA - now)	Tertiary (65-1.8 MYA)	Paleocene (65-54 MYA)
			Eocene (54-38 MYA)
			Oligocene (38-23 MYA)
			Miocene (23-5 MYA)
			Pliocene (5-1.8 MYA)
		Quaternary (1.8 MYA - now)	Pleistocene (1.8-0.01 MYA)
			Holocene (0.01 MYA - now)

The Paleocene, the Eocene, and the Oligocene are also collectively known as the Paleogene. The Miocene and the Pliocene are also collectively known as the Neogene.

These names differ across different countries; in particular, the division of the Carboniferous period into Mississippian and Pennsylvanian is purely a North American distinction.

Human time periods

The "human" timescale covers the time that humans have existed, usually taken to be from about 250,000 years ago - when Homo Sapiens[?] began to develop. It is broadly divided into prehistorical (before history began to be recorded) and historical periods (when written records began to be kept).

Calendar systems