Greyjan the Sane was the Time Lord who served as Lord President of Gallifrey for the shortest term in the planet's history.
Greyjan served as the Time Lord president between the Earth dates 2 September 1752 and 14 September 1752. These days were in fact the eleven non-existent days that had been created from nothing by the change from the Julian to the Gregorian calendar, which Faction Paradox had "purchased" from Earth's governments and used in the creation of their dimension, the Eleven-Day Empire. This made Greyjan especially vulnerable to their machinations. Among other notorious features of his biography, he studied paradoxes and committed suicide.
Greyjan the Sane was recreated using a Remembrance Tank, Gallifreyan biodata and his mind and memories that existed within the Matrix, by a Faction Paradox cultist. (PROSE: The Ancestor Cell)