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The categorization of time into discrete named blocks is called periodization. This is a list of such 'named time periods' as defined in various fields of study. Major categorization systems include 'cosmological' (concerning the various time periods in the origin and evolution of our universe), 'geological' (concerning time periods in the origin and evolution of earth ) and 'historical' (concerning time periods in the origin, evolution of mankind).

Contents

Human time periods

Prehistorical periods

Historical periods

Calendar systems

Mythological and astrological time periods

Cosmological time periods

13.7 billion years ago: The Big Bang.

Formation of Population III stars

Formation of Population II stars

5 Billion Years ago - Formation of Population I stars

Geologic time periods

See also

References

Human time periods

Based on current and debatable evidence, the human race has found its origins starting from about 250,000 years ago - when ''homo'' 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).

Prehistorical periods

Main articles: List of archaeological periods

In archaeology and anthropology, prehistory is subdivided around the three-age system.

★ Paleolithic Age

★ The Neolithic Age

★ The Bronze Age
The dates for each age can vary by region, although the beginning of Mesolithic is usually considered to correspond to the beginning of the Holocene epoch on the geologic time scale at the end of the most recent Ice age, about 9400 BC.

Historical periods

★ Antiquity

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★ Iron Age

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★ Mesopotamia 6000 BC - 1100 BC

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★ Indus Valley Civilization 3300 BC - 1300 BC

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★ Old Kingdom (Egypt, 3000 BC - 2000 BC)

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★ Middle Kingdom (Egypt, 2000 BC - 1300 BC)

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★ Shang Dynasty (China 1800 BC - 1200 BC

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★ New Kingdom (Egypt, 1300 BC - 700 BC)

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★ Zhou Dynasty (China 1200 BC - 500 BC)

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★ (Ancient Greece, c:a 1000 BC-, see Timeline of Ancient Greece)

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★ Ancient Rome 509 BC - 476)

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★ Period of the Three Kingdoms (China, 220 - 280)

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★ Dark Age {Europe, 4th century - 900}

★ Middle Ages (Europe, 5th century - 15th century)

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★ Viking Age (Scandinavia, Europe, 793 - 1066)

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★ Nara period (Japan, 709 - 795)

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★ Period of Five Dynasties and Ten Kingdoms (China, 907 - 960)

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★ Fatih Sultan Mehmet (Istanbul, 1453)

★ Early Modern (Europe, 14th century - 18th century)

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★ The Renaissance (Europe, 14th century - 16th century)

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★ Age of Discovery (or Exploration) (Europe, 15th century - 17th century)

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★ Elizabethan period (United Kingdom, 1558 - 1603)

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★ The Protestant Reformation (Europe, 16th century)

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★ The Age of Enlightenment (Europe,18th century)

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★ Tokugawa shogunate (Japan, 1603 - 1868)

★ Modern (Europe, 18th century - 20th century)

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★ Industrial Revolution (Europe, United States, elsewhere 18th and 19th centuries)

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★ Napoleonic Era (1799 - 1815)

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★ Victorian era (United Kingdom, 1837 - 1901)

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★ Edwardian period (United Kingdom, 1901 - 1910)

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★ Meiji era (Japan, 1868 - 1912)

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★ Machine Age(1900 - 1945)

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★ Electric age^[1]

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★ World War I (Much of Earth, 1914 - 1918)

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★ Interwar period (Earth, 1918 - 1939 or 1937)

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★ World War II (Earth, 1937 or 1939 - 1945)

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★ Atomic Age (after 1945)

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★ Cold War (Soviet Union and United States, as well their allied states, 1945 - 1989)

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★ Space Age (after 1957)

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★ Information Age (1971 - Present)

Calendar systems

Various societies in the past have created calendars to record events, such as religious observances and agricultural tasks. A common characteristic of most known calendars is that they measure time in relation to a particular point in history, known as the epoch date. A period between epoch dates is known as a calendar era.

Mythological and astrological time periods

★ Astrological ages

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★ Age of Taurus

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★ Age of Aries

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★ Age of Pisces

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★ Age of Aquarius

★ Greek mythology

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★ Golden Age, self-sufficient

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★ Silver Age, self-indulgent

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★ Bronze Age, warlike

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★ Heroic Age, nobly aspirant

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★ Iron Age, violent

★ Aztec mythology

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★ Nahui-Ocelotl, Destroyed by Jaguars

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★ Nahui-Ehécatl, Destroyed by Hurricane

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★ Nahuiquiahuitl, Destroyed by rain of Fire

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★ Nahui-Atl, Destroyed by Flood

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★ Nahui-Ollin, Destroyed by Earthquakes

Cosmological time periods

13.7 billion years ago: The Big Bang.

Main articles: Timeline of the Big Bang

Because of the scales involved (both very large and very small), cosmological time periods are usually described in seconds. In this table, each row is defined in seconds after the Big Bang, with earliest at the top of the chart.

'Seconds after the Big Bang'	'Period'
5.4 × 10−44	Planck time
10−43 to 10−35	Planck Epoch
10−35 to 10−33	Inflationary epoch
10−35 to 10−12	Epoch of Grand Unification
10−12 to 10−6	Electroweak Epoch
10−6 to 100	Hadron Epoch
1 to 100	Lepton Epoch

100 seconds to 300,000 years after the big bang - Epoch of Nucleosynthesis
300,000 years on from the Big Bang - Epoch of Galaxies

Formation of Population III stars

The first stars were formed from the Hydrogen and Helium formed in the Big Bang were short lived massive Population III stars. Nuclear processes in these stars converted the Hydrogen and Helium into metals and other heavier elements. As the Population III stars died these heavier elements were released.

Formation of Population II stars

Population II stars contain metals formed in the Population III stars. These were longer lived than the Population III stars and some of them are still around. In addition to the metals these inherited from the Population III stars the Population II stars also formed metals by nuclear reactions and when the stars died much of that material was returned to be used as the building blocks for the next generation of stars.

5 Billion Years ago - Formation of Population I stars

Population I stars are also known as metal rich stars. Our own sun is a Population I star and was formed about 5 billion years ago.

Geologic time periods

Main articles: Geologic time scale, List of Global Boundary Stratotype Sections and Points

The geologic time scale covers the extent of the existence of Earth, from about 4600 million years ago to the present day. It is marked by Global Boundary Stratotype Sections and Points. Geologic time units are (in order of descending specificity) eons, eras, periods, epochs, and ages; and the corresponding chronostratigraphic units, which measure "rock-time", are eonothems, erathems, systems, series, and stages.
The second and third timelines are each subsections of their preceding timeline as indicated by asterisks. The Cenozoic is sometimes divided into the Quaternary and Tertiary periods, although their use is no longer official.

See also

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

★ Exponential timeline shows all history on one page in ten lines.

★ List of timelines

★ List of fossil sites ''(with link directory)''

References

1. Marshall McLuhan (1964) ''Understanding Media'', p.13 [1]