when did ayatollah khomeini come to power

Ayatollah Ruhollah Khomeini effectively came to power in 1979 , during and immediately after the Iranian Revolution.

• He returned from exile to Iran on 1 February 1979 , greeted by massive crowds.
• By 11 February 1979 , the Shah’s regime had collapsed and Khomeini had assumed effective leadership of the new revolutionary order.
• In March–April 1979 , a national referendum approved the creation of an Islamic Republic , with Khomeini as its ultimate political and religious authority for life.
• By December 1979 , the new constitution formally established him as Supreme Leader (rahbar), cementing his position as head of state.

So, in simple terms: Khomeini came to power in 1979 , with his de facto rule beginning in February and his formal status as Supreme Leader solidified by the end of that year.