The mathematical aberration of the Gregorian chronology's missing "year zero" retains enduring potential to sow confusion in studies of paleoclimatology and environmental ancient history. The possibility of dating error is especially high when pre-Common Era proxy evidence from tree rings, ice cores, radiocarbon dates, and documentary sources is integrated. This calls for renewed vigilance, with systematic reference to astronomical time (including year zero) or, at the very least, clarification of the dating scheme(s) employed in individual studies.

Department of Geography Faculty of Science Masaryk University 613 00 Brno Czech Republic

Department of Geography University of Cambridge Cambridge CB2 3EN United Kingdom;

Forest Dynamics Research Unit Swiss Federal Research Institute WSL 8903 Birmensdorf Switzerland

Global Change Research Institute Czech Academy of Sciences 603 00 Brno Czech Republic

McDonald Institute for Archaeological Research Cambridge CB2 3ER United Kingdom

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