On This Day:  January 29

A.D. 904 -- Start of the reign of Pope Sergius III, in­volved in a com­plex for­mu­la of both a slain pope and an­tipope, re-ex­e­cu­tion of a dead pope, and the birth of a fu­ture pope, with the fi­nal sum of ze­ro.

28 | January | 30