The Geologic Calendar is a scale in which the geological timespan of the Earth is mapped onto a calendrical year; that is to say, the day one of the Earth took place on a geologic January 1 at precisely midnight, and today's date and time is December 31 at midnight.[1] On this calendar, the inferred appearance of the first living single-celled organisms, prokaryotes, occurred on a geologic February 25 around 12:30pm to 1:07pm,[2] dinosaurs first appeared on December 13, the first flower plants on December 22 and the first primates on December 28 at about 9:43pm. The first anatomically modern humans did not arrive until around 11:48 p.m. on New Year's Eve, and all of human history since the end of the last ice-age occurred in the last 82.2 seconds before midnight of the new year.
A variation of this analogy instead compresses Earth's 4.6 billion year-old history into a single day: While the Earth still forms at midnight, and the present day is also represented by midnight, the first life on Earth would appear at 4:00am, dinosaurs would appear at 10:00pm, the first flowers 10:30pm, the first primates 11:30pm, and modern humans would not appear until the last two seconds of 11:59pm.
A third analogy, created by University of Washington paleontologist Peter Ward and astronomer Donald Brownlee, who are both famous for their Rare Earth hypothesis, for their book The Life and Death of Planet Earth, alters the calendar so it includes the Earth's future leading up to the Sun's death in the next 5 billion years. As a result, each month now represents 1 of 12 billion years of the Earth's life. According to this calendar, the first life appears in January, and the first animals first appeared in May, with the present day taking place on May 18. Even though the Sun won't destroy Earth until December 31, all animals will die out by the end of May.
Use of the geologic calendar as a conceptual aid dates back at least to the mid 20th century, for example in Richard Carrington's 1956 book A Guide to Earth History[3] and Gove Hambidge's 1941 chapter in the book Climate and Man.[4] Some authors also used a similar imaginative device of compressing the entire history of the human species to a shorter period, whether a single year as in Ramsay Muir's 1940 book Civilization and Liberty,[5] or fifty-year span as in James Harvey Robinson's 1921 book The Mind in the Making.[6]
^Kentucky Geological Survey (2011). "The Geological Time Scale v.3" (PDF). Kentucky Geological Survey. Retrieved 2013-06-03.
^"Geologic History Compressed into 1 Calendar Year". Timetoast. 2010. Retrieved 2013-06-03.
^Carrington, Richard (1956). A Guide to Earth History. Penguin Books. p. 64-65.
^Hambidge, Gove (1941). Climate and Man. p. 7.
^Muir, Ramsay (1940). Civilization and Liberty. Jonathan Cape. p. 15.
^Robinson, James Harvey (1921). The Mind in the Making. Harper & Brothers Publishing. p. 82-83.
The GeologicCalendar is a scale in which the geological timespan of the Earth is mapped onto a calendrical year; that is to say, the day one of the Earth...
similar analogy used to visualize the geologic time scale and the history of life on Earth is the GeologicCalendar. Date in year calculated from formula...
the table of geologic time presented in this article conforms to the nomenclature, ages, and colour codes set forth by the ICS. The geologic time scale...
period (mainly prehistoric), where "geologic era" refers to well-defined time spans. The next-larger division of geologic time is the eon. The Phanerozoic...
A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A date is the designation...
Calendar of saints Advent calendar Wall calendarGeologicCalendar Cosmic Calendar Lunar calendar World calendar Parker, Richard A., "The Calendars of...
The Holocene calendar, also known as the Holocene Era or Human Era (HE), is a year numbering system that adds exactly 10,000 years to the currently dominant...
A lunisolar calendar is a calendar in many cultures, incorporating lunar calendars and solar calendars. The date of lunisolar calendars therefore indicates...
Hijri calendar (Arabic: ٱلتَّقْوِيم ٱلْهِجْرِيّ, romanized: al-taqwīm al-hijrī), or Arabic calendar also known in English as the Muslim calendar and Islamic...
The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull Inter gravissimas...
before and after a calendar change, respectively. Usually, they refer to the change from the Julian calendar to the Gregorian calendar as enacted in various...
A lunar calendar is a calendar based on the monthly cycles of the Moon's phases (synodic months, lunations), in contrast to solar calendars, whose annual...
Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year (without exception). The Julian calendar is still...
year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the...
The Hebrew calendar (Hebrew: הַלּוּחַ הָעִבְרִי, romanized: HaLuah HaIvri), also called the Jewish calendar, is a lunisolar calendar used today for Jewish...
chronology or historiography Geologic time scale – System that relates geologic strata to time Lunisolar calendar – Calendar with lunar month, solar year...
A calendar era is the period of time elapsed since one epoch of a calendar and, if it exists, before the next one. For example, it is the year 2024 as...
Christ (BC) are used when designating years in the Julian and Gregorian calendars. The term anno Domini is Medieval Latin and means "in the year of the...
Roman calendar was the calendar used by the Roman Kingdom and Roman Republic. Although the term is primarily used for Rome's pre-Julian calendars, it is...
in astronomy, biology, chemistry, and geology: 2009 flu pandemic timeline Chronology of the universe Geologic time scale Timeline of evolutionary history...
into six geologic periods: from oldest to youngest, they are the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. Geologically, the Paleozoic...
a specified chronology in archaeology and geology. Some scientists prefer the terms chronometric or calendar dating, as use of the word "absolute" implies...
shorter than 13 of them (about 383.90 days). In a Metonic calendar (a type of lunisolar calendar), there are twelve years of 12 lunar months and seven years...
The adoption of the Gregorian Calendar was an event in the early modern history of most cultures and societies, marking a change from their traditional...
The World Calendar is a proposed reform of the Gregorian calendar created by Elisabeth Achelis of Brooklyn, New York in 1930. The World Calendar is a 12-month...
reforms of Julius Caesar in 45 BC put the Roman world on a solar calendar. This Julian calendar was faulty in that its intercalation still allowed the astronomical...
The proleptic Julian calendar is produced by extending the Julian calendar backwards to dates preceding AD 8 when the quadrennial leap year stabilized...
derive absolute age dates for all fossil assemblages and determine the geologic history of the Earth and extraterrestrial bodies. By measuring the amount...
contradicts the hypothesis and it failed to gain the support of historians, and calendars in other European countries, most of Asia and parts of pre-Columbian America...
Global Information