The Western or Christian calendar is divided into two parts separated by an imaginary zero point representing the birth of Christ. Because radiocarbon years are not equivalent to calendar or solar years, they have to be transformed by computer or by using a graph to calendar years. Relative dating techniques place items or events in a temporal sequence relative to one another without actually giving the specific years involved. For example, some artifacts are much older than other artifacts either by material and technology or by position in the ground. In none of these situations do we actually know the dates of events or how many years may separate them.
Archaeologists are quite fond of using a relative scale divided into early, middle, and late.
Independent dating techniques are those such as radiocarbon and dendrochronology that are based on processes independent of human behavior. Radiocarbon, for example, measures the rate of atomic decay in isotopes of carbon after a plant or animal has died. Intrinsic dating techniques measure factors that are dependent on the involvement or direct behavior of human beings. Only people make calendars to record time that can be used to inscribe buildings, monuments, and coins. Unfortunately, unlike the Classic Maya of southern Mexico and Guatemala, no calendars have survived to mark events in the prehistoric Southwest.