Complex sentence: He served as premier of the colony from 1865 to 1867, again from 1870 to 1872 and was premier of PEI in 1873 when the island joined Canadian confederation.
Split into simpler sentences: He served as premier of the colony from 1865 to 1867, and from 1870 to 1872. He was premier of PEI in 1873 when the island joined Canadian confederation.