Calendar Reform and World Chronology: Pierre De Lille's Tria Calendaria Parva (1529).

This essay explores the astronomical works of Pierre de Lille, a little-known French participant in the debates on calendar reform during the Fifth Lateran Council (1512–1517). It argues that astrological ideas coupled with eschatological beliefs motivated his astronomical propositions to reform the Julian calendar. De Lille conceived the calendar solar year as a unit of a great cosmic year spanning 7,153 years, the duration that he assigned to the now-obsolete theory of the motion of trepidation of the eighth sphere. Although his use of this astronomical model for astrological speculations about world chronology was not new, de Lille gave an original and bold reply to Pico della Mirandola's devastating critique of astrology. The astronomical model and its astrological implications were eventually contested at the court and in academia in France, but the alliance of chronology, astrology, and apocalypticism was to play a major role during the second half of the sixteenth century in Lutheran thought. [ABSTRACT FROM AUTHOR]