kiloyear

Kiloyear is a unit of time equal to 1,000 years. It is formed from the prefix kilo- meaning thousand and the unit year, and is commonly abbreviated kyr. In some scientific contexts, the related term kiloannum (ka) is used; kyr and ka are often treated as interchangeable when referring to elapsed time or dated ages, though field conventions vary and ka is sometimes explicitly tied to years before present (BP).

Usage and context: Kiloyears are widely used in geology, paleoclimatology, archaeology, and related disciplines to describe long timescales, such as ages of events, durations of climatic episodes, or stages in a geologic or evolutionary record. For example, statements like “the event occurred about 20 kyr ago” express a time span of twenty kiloyears. In radiometric dating and geochronology, ka or kyr may appear with BP (ka BP or kyr BP) to indicate years before present, while kyr alone can denote a time interval or an age without an explicit reference to present.

Length and notation: A kiloyear is 1,000 calendar years. If expressed in seconds using a Julian year (exactly 365.25 days), 1 kyr equals 31,557,600,000 seconds. The unit is not part of the SI system; in precise technical work, researchers may specify the year convention used (for example, Julian year) to avoid ambiguity.

See also: Year, Kiloyear in geochronology, Kiloannum, Geologic time scale, Myr, Gyr.