John Calvin was not a professional historian. He was training to be a lawyer before settling in Geneva. Among other things, He became a Pastor and the magisterial governor of Geneva. He was one of the best (if not the best) theologian the church has ever seen, so he probably had extensive knowledge of church history, although I doubt this would qualify him as a historian.
John Calvin Doyle's birth name is John Calvin Doyle.
John Davies - historian - was born in 1938.
John Vincent - historian - was born in 1937.
John Bell - historian - was born in 1952.
John MacLean - historian - was born in 1811.
John Weaver - historian - died in 1965.
John Ramsden - historian - died in 2009.
John Ramsden - historian - was born in 1947.
John Morris - historian - was born in 1913.
John Mooney - historian - was born in 1862.
John Mooney - historian - died in 1950.
John North - historian - died in 2008.