chronology

Chronology is the science and art of arranging events in their order of occurrence in time. It provides the framework for understanding sequences of events across history, geology, archaeology, astronomy, and climatology. The word derives from Greek chrōn, time, and logos, study.

Chronology can be absolute, assigning specific dates or calendar-era ranges to events, or relative, placing events in a sequence without fixed dates. Absolute dating relies on physical or astronomical data, while relative dating relies on contextual relationships between findings and other dated events.

Common absolute dating methods include radiocarbon dating, dendrochronology, potassium-argon dating, thermoluminescence, and uranium-series dating. Relative methods include stratigraphy, biostratigraphy, index fossils, typology, and cross-dating between sites. Calibrations and uncertainties are inherent, requiring multiple lines of evidence to produce reliable timelines.

Calendars and time systems—such as Julian, Gregorian, and various lunar or luni-solar schemes—shape chronological work. Modern practice typically uses B.C.E./C.E. or B.P., with explicit calibration and error ranges to maintain clarity across cultures and eras.

Applications of chronology include constructing historical timelines, correlating events across regions, and interpreting geological and climatic records. In archaeology, paleontology, history, and astronomy, robust chronological frameworks are essential for testing hypotheses about causality, development, and major transitions. Key concepts include terminus ante quem and terminus post quem, which establish outer bounds on dating estimates, and the use of horizon events for cross-dating.