Chances are, right now, you have a Gregorian calendar stuck to your wall.This calendar, with the months January through December, is a business standard used in many places round the world to define the year: one which hearkens back to Christian and Roman Imperial precedents.Paleontology seeks to map out how life evolved across geologic time.

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These various chronologies and their inherent inconsistencies, known as ‘relative dates,’ are a constant series of hurdles in the quest of historians and archaeologists to record mankind’s existence on earth.

However, in the 1940s, the organization of time was transformed by the revelation of radiometric dating and the subsequent creation of a scientific chronology of humankind, known as ‘absolute dating’.

The layers of sedimentary rock, or strata, can be seen as horizontal bands of differently colored or differently structured materials exposed in this cliff.

The deeper layers are older than the layers found at the top, which aids in determining the relative age of fossils found within the strata. Such index fossils must be distinctive, globally distributed, and occupy a short time range to be useful.

Different cultures around the world record time in different fashions.

According to the Gregorian calendar, it is the year 2009 AD. The Kaliyuga Hindu Calendar maintains it is 5110, the Islamic calendar 1430 and the Persian, 2630.There are several different methods for estimating the ages of fossils, including: Paleontologists rely on stratigraphy to date fossils.Stratigraphy is the science of understanding the strata, or layers, that form the sedimentary record.If a fossil is found between two layers of rock whose ages are known, the fossil's age is thought to be between those two known ages.Because rock sequences are not continuous, but may be broken up by faults or periods of erosion, it is difficult to match up rock beds that are not directly adjacent.The radioactive carbon has six protons and eight neutrons in its nucleus, giving it a total atomic mass of 14.