Glossary Archaeological method and dating
Calibrated date
Also called: cal BC, cal BCE, cal BP
A radiocarbon result converted into calendar years using a calibration curve, usually written cal BC, cal BCE or cal BP.
The amount of carbon-14 in the atmosphere has varied over time, so a raw radiocarbon age does not equal calendar years. Laboratories convert it using a calibration curve built from tree rings and other dated records, and give the result as a range with a probability, for example 2198–1771 cal BC at 95 per cent. Older publications often quote uncalibrated ages, sometimes marked with a lower-case bc, which can be centuries too young.
The difference matters in Cyprus. Dikaios's 3500–3200 BC for the pottery of Sotira is an uncalibrated figure; calibrated, the Ceramic Neolithic falls roughly between 4500/4700 and 3900 BCE (Combed Ware). Many projects now combine groups of dates with the known order of layers in Bayesian statistical models, which narrow the ranges, as at Akrotiri-Aetokremnos (Cyprus Before Humans).
Related terms
- Radiocarbon dating
A scientific method that dates once-living material such as charcoal, seeds and bone by measuring the decay of the carbon-14 it contains.
- Absolute chronology
A chronology expressed in calendar years (BCE, CE or years before present), fixed by scientific dating or by links to written history.
- Stratum
A single layer of deposit on an archaeological site, usually numbered by the excavator; the plural is strata.