The Mayan calendar used 3114 BC as their reference.More recently is the radiocarbon date of 1950 AD or before present, BP.
It should be noted that a BP notation is also used in other dating techniques but is defined differently, as in the case of thermoluminescence dating wherein BP is defined as AD 1980.
dating, the determination of the age of an object, of a natural phenomenon, or of a series of events.
There are two basic types of dating methods, relative and absolute.
In relative dating, the temporal order of a sequence of events is determined, allowing the investigator to surmise whether a particular object or event is older or younger than, or occurred before or after, another object or event.
In absolute or chronometric dating, the investigator establishes the age of an object or event in calendar years.