During the past 30 years, since the first edition of this publication (Curry et al. 1978), both the absolute chronology of the Tertiary, and its calibration to other geochronological and biochronological events, have been progressively refined and stabilized. This has resulted from resolution of the relationships of successions in different areas, largely through biostratigraphy, magnetostratigraphy and improved radiometric dating. Important milestones during the earlier part of this period have been syntheses by Berggren et al. (1985, 1995), Haq et al. (1987, 1988) and Harland (1990). The Berggren et al. (1995) publication incorporated a rigorous re-evaluation of key planktonic foraminiferid and calcareous nannoplankton datums, and their calibration to the magnetostratigraphic and geochronological scale. It also incorporated the first astronomically tuned calibration of the timescale, which had been extended ‘downwards’ from the Pleistocene through the Pliocene by this time. The Berggren et al. (1995) timescale remained the standard reference for almost a decade.