The pattern of tree rings visible in a sample from a timber beam is compared to the sequence for the area, where each ring is dated to a particular season and year.
When there is a match between the sample and the sequence, it reveals the date when the tree was cut down (and the tree stopped growing).
His initial findings are that the trees used for timber at Wymering Manor were most probably felled in the .
This makes construction of the original part of the present house most likely in 1581 or within a year or two of this date, while the wood was still green and easily worked.
The oak slice from the Taylor stone Lancashire style ground barn located just west of West Chester in Chester County, Pennsylvania was dendro-dated to 1752.
This date established the structure to be the earliest basically intact and scientifically verified barn in all of Pennsylvania.
Any piece of wood from the present day backwards will usually overlap its tree ring pattern with an older piece - e.g.
a tree felled in autumn 1945 may contain rings in its early (inner) pattern which will match to the outer (later) pattern of a tree felled in spring 1870. Many years of painstaking research have now compiled detailed sequences for many parts of the world, in Britain covering the last 7,300 years.
Although the science of dendrochronology was first formulated about 1905, it has only until very recently, perhaps since 2000, that the science has gained much popularity with private homeowners.
Before that time, the science, art and philosophy of dendrochronology – aka – dendro-dating – was mostly limited to the determination of ages of buildings under the control of certain public and some private institutions.