The process by which an archaeologist determines dates for objects, deposits, buildings, etc., in an attempt to situate a given phenomenon in time. Relative dating, in which the order of certain events is determined, must be distinguished from absolute dating, in which figures in solar years (often with some necessary margin of error) can be applied to a particular event. Unless tied to historical records, dating by archaeological methods can only be relative - such as stratigraphy, typology, cross-dating, and sequence dating. Absolute dating, with some reservation, is provided by dendrochronology, varve dating, thermoluminescence, potassium-argon dating, and, most important presently, radiocarbon dating. Some relative dating can be calibrated by these or by historical methods to give a close approximation to absolute dates - archaeomagnetism, obsidian hydration dating, and pollen analysis. Still others remain strictly relative - collagen content, fluorine and nitrogen test, and radiometric assay. Other methods include: coin dating, seriation, and amino-acid racemization. The methods have varying applications, accuracy, range, and cost. Many new techniques are being developed and tested.