The occurrence of atmospheric14C variations complicates calibration,ie, the translation of14C ages into real calendar ages. The procedure of wiggle matching, however, allows very precise calibration, by matching known14C variations with wiggles in the floating chronology. In principle, wiggle matching can also be applied to a series of14C dates from organic (peat) deposits. Where, in general,14C ages are required at short distances and on small samples, dating by14C accelerator mass spectrometry (AMS) is required.