Chronology

Chronology (from Latin chronologia, from Ancient Greek , chrónos, "time"; and -λογία, ) is the science of arranging events in their order of occurrence in time. Consider, for example, the use of a timeline or sequence of events. It is also "the determination of the actual temporal sequence of past events".

Chronology is part of periodization. It is also part of the discipline of history, including earth history, the earth sciences, and study of the geologic time scale.

Chronology is the science of locating historical events in time. It relies upon chronometry, which is also known as timekeeping, and historiography, which examines the writing of history and the use of historical methods. Radiocarbon dating estimates the age of formerly living things by measuring the proportion of carbon-14 isotope in their carbon content. Dendrochronology estimates the age of trees by correlation of the various growth rings in their wood to known year-by-year reference sequences in the region to reflect year-to-year climatic variation. Dendrochronology is used in turn as a calibration reference for radiocarbon dating curves.

The familiar terms calendar and era (within the meaning of a coherent system of numbered calendar years) concern two complementary fundamental concepts of chronology. For example, during eight centuries the calendar belonging to the Christian era, which era was taken in use in the 8th century by Bede, was the Julian calendar, but after the year 1582 it was the Gregorian calendar. Dionysius Exiguus (about the year 500) was the founder of that era, which is nowadays the most widespread dating system on earth. An epoch is the date (year usually) when an era begins.

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