Dating of oak structures and artifacts in Northwest Europe posed problems that have largely been solved by analysis of the ring-width patterns of hundreds of trees felled in historic or recent times. It has been found that the pattern of oaks of slow growth from areas adjacent to the North Sea became different to that of oaks grown in the cool/wetter areas at higher altitudes in central Germany or western Britain after ca. A.D. 1250 when a drier continental climate prevailed. The implications on methodology and chronology formation are given with an explanation of the unsuitability of applying to Eurpoean oak the practice followed at Tuscon for dendrochronology of conifers.