When it comes to dating archaeological samples, several timescale problems arise.For example, Christian time counts the birth of Christ as the beginning, AD 1 (Anno Domini); everything that occurred before Christ is counted backwards from AD as BC (Before Christ).Rodents, for example, can create havoc in a site by moving items from one context to another.Natural disasters like floods can sweep away top layers of sites to other locations.The extra neutrons in Carbon-14’s case make it radioactive (thus the term, radiocarbon).
In 11,460 years, half of the 50% will remain, or 25%, and so on.
Long tree-ring sequences have been developed throughout the world and can be used to check and calibrate radiocarbon dates.
An extensive tree-ring sequence from the present to 6700 BC was developed in Arizona using California bristlecone pine (), some of which are 4900 years old, making them the oldest living things on earth.
The Greeks consider the first Olympic Games as the beginning or 776 BC.
The Muslims count the Prophet’s departure from Mecca, or the Hegira, as their beginning at AD 662.