Dating methods are the means by which archaeologists establish chronology. The more dating methods we use to construct a chronology, the more likely it is that the chronology will be reliable.
The most universal dating method in archaeology is a relative dating method: dating by association. At it simplest, this means recognising an artefact or structure as belonging to a known type of a particular date. Where there is a significant number of these associations, the dating information they give us becomes more reliable - individual cases can be misleading - artefacts, for instance, may be residual (belonging to an earlier period but present in a later context due to redeposition). The more associations we have, the easier it is to see such problems in the evidence, and therefore the more likely the site chronology is to be correct.
Absolute dating methods include radiocarbon, dendrochronology, TL/luminescence dating, archaeomagnetic dating and a variety of less common techniques. All of these have two things in common: Firstly they are only possible when the right sort of material is present (for example, there is no possibility of using radiocarbon or dendrochronology when there is no organic matter or preserved wood available); secondly, they are all comparatively expensive to carry out and the results may not provide the kind of answer that the archaeologist is trying to find. Archaeologists must depend on their experience to guide them as to the most effective use of resources in commissioning scientific dating programmes. Often, this only becomes clear at the post-excavation stage. It is always good practice therefore, to take a wide range of samples of any datable material during excavation so that there will be maximum potential for a dating programme at a subsequent stage of the work. Ideally, relative and absolute dating methods should complement each other and provide a means of cross-checking or control. Any conclusion on dating drawn from just one unsupported technique is usually regarded as unreliable by other archaeologists.