In which year did Fidel Castro become president of Cuba?

Fidel Castro officially became the Prime Minister of Cuba in 1959 after the successful revolution that overthrew the Batista regime. However, in 1976, significant constitutional reforms were made in Cuba, and the position of president was re-established. Castro transitioned to this role, thus becoming the President of the Council of State and the Council of Ministers. This marked a formal recognition of his leadership in the new government structure. The shift to the presidency in 1976 is crucial in understanding his political evolution and the consolidation of power in Cuba during that period.

The other years listed do not align with the official assumption of the presidential role. Castro had already been in power for many years by 1962, and the years 1988 and 1990 came after he had already established his presidency.