Any technique of dating that relies on chronological measurement such as calendars, radiocarbon dates, etc. and which give the result in calendar years before the present, or B.P. Most of these techniques produce results with a standard deviation, but they have a relationship to the calendar which relative dating techniques do not. Among the most useful chronometric dating techniques are radiocarbon dating, potassium argon dating, and thermoluminescence dating. Dendrochronology, the relationship of dated ancient trees with live trees has no standard deviation and is the most accurate of all, though not universally applicable. Chronometric dating has developed in the last 30 years and has revolutionized archaeology.