Original: The term Commonwealth is , however , loosely used to describe the system of government during the whole of 1649 to 1660 , when England was de facto , and arguably de jure , a republic ( or , to monarchists , under the English Interregnum ) .
Simplified: The term Commonwealth is , however , loosely used to describe the system of government during the whole of 1649 to 1660 , the years of the English Interregnum .