How long did the Puritans rule England under the Commonwealth?

The duration of Puritan rule in England under the Commonwealth was indeed approximately 20 years. This period began in 1649 when Charles I was executed, leading to the establishment of the Commonwealth, a republican form of government. The rule was then marked primarily by Oliver Cromwell's leadership as Lord Protector, which lasted until his death in 1658.

The Commonwealth officially ended in 1660 with the Restoration of the monarchy under Charles II. Therefore, the timing of the Puritan regime aligns well with the duration of nearly 20 years, from 1649 to 1660, which encapsulates the significant historical transformation experienced during that period.