epoch

1. A period marked by distinctive character or reckoned from a fixed point or event (synset 115273375)
   is a type of: period, period of time, time period - an amount of time
   subtypes:

   • day - an era of existence or influence
   • age, historic period - an era of history having some distinctive feature
   • modern era - the present or recent times
   specific instances:

   • caliphate - the era of Islam's ascendancy from the death of Mohammed until the 13th century; some Moslems still maintain that the Moslem world must always have a calif as head of the community
   • christian era, common era - the time period beginning with the supposed year of Christ's birth
   same as: era
2. (astronomy) an arbitrarily fixed date that is the point in time relative to which information (as coordinates of a celestial body) is recorded (synset 115321930)
   referred to in: astronomy, uranology - the branch of physics that studies celestial bodies and the universe as a whole
   is a type of: date - the particular day, month, or year (usually according to the Gregorian calendar) that an event occurred
   same as: date of reference
3. A unit of geological time that is a subdivision of a period and is itself divided into ages (synset 115273080)
   is a type of: geologic time, geological time - the time of the physical formation and development of the earth (especially prior to human history)
   specific instances:

   • holocene, holocene epoch, recent, recent epoch - approximately the last 10,000 years
   • glacial epoch, pleistocene, pleistocene epoch - from two million to 11 thousand years ago; extensive glaciation of the northern hemisphere; the time of human evolution
   • pliocene, pliocene epoch - from 13 million to 2 million years ago; growth of mountains; cooling of climate; more and larger mammals
   • miocene, miocene epoch - from 25 million to 13 million years ago; appearance of grazing mammals
   • oligocene, oligocene epoch - from 40 million to 25 million years ago; appearance of sabertoothed cats
   • eocene, eocene epoch - from 58 million to 40 million years ago; presence of modern mammals
   • paleocene, paleocene epoch - from 63 million to 58 million years ago; appearance of birds and earliest mammals
   is a part of: geological period, period - a unit of geological time during which a system of rocks formed

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