Therefore, if you measure the amount of 14C in a dead organism, you can calculate out how long ago it died. In 14C every 5,730 years half of it is gone. The half-life of an isotope like 14C is the time it takes for half of it to decay away. When an organism dies, the 14C slowly decays at a known rate called its “half-life.”

All living organisms contain the gas Carbon 14 (C14 or 14C). Radiocarbon dating was discovered in the 1940s. Radiometric dating techniques are those that provide absolute dates based on the decay of radioactive isotopes. The use of BP by archaeologists, geologists, and other scientists, refers to radiocarbon ages and results from other radiometric dating techniques. The initials ‘BP’ stand for ‘years before present’. As with ‘CE’, it removes the explicit reference to Christ, but is still equivalent to ‘BC’ in date. As with ‘bc’, the lowercase ‘bc’ often means that the date used is an uncalibrated date. This signifies the pre-Christian era in the Gregorian calendar. First used almost 400 years ago, it has become especially popular from the late twentieth century to emphasise secularism or sensitivity to non-Christians. But, it removes the explicit claim of Anno Domini which means ‘year of our Lord’. ‘CE’ is equivalent to ‘AD’ as a date and places the ‘common’ or ‘current’ era as being from the suggested birth of Christ at 1 AD (e.g. the Battle of Hastings was in AD 1066), or sometimes it means calibrated radiocarbon age in calendar years. ‘AD’ in upper case can mean the date stands for a historical date (e.g. If lower case letters are used, this often means that the date is based on an uncalibrated radiocarbon date (see below for date calibrations). ‘AD’ is generally written in upper case letters. (The date was calculated about 500 years after the event, so was a broad estimate.) This is the Christian era in the Gregorian calendar, starting from 1 AD as the year in which Christ was believed to have been born. So, what’s the difference between them, and why use both? AD, ad, CE

Seeing ‘bp’, or ‘BP’, or ‘BC’ is common, and they are often used together.

In almost all archaeology books and articles the authors use dates.

What is the meaning of ad