Complex sentence: He was twice provisional governor of the then independent Province of Buenos Aires, a first time from September 11 to October 31,1852, and the second time from December 7,1852 until his death.
Split into simpler sentences: He was twice provisional governor of the then independent Province of Buenos Aires. His first term spanning from September 11 to October 31,1852, and the second term from December 7,1852 until his death.