Environmental Archaeology, A Guide to the Theory and Practice of Methods, from Sampling and Recovery to Post-excavation (second edition), published by English Heritage (now Historic England) in 2011, defines dendrochronology as: ‘tree-ring dating.’
A tree gains another ring each year as it grows, with the thickness depending on the amount of growth. All the same trees in a region are likely to display the same chronological growth pattern. Therefore, by plotting the relative thickness of these rings, a clearly identifiable sequence of variations may emerge which can act like a date stamp for each period.
The advantage of dendrochronology is its objectivity. Where analysis results in a clear match with the master chronology the results are completely accurate and reliable.