In what year did Spaniards vote for the Constitution that is still in force today?

✓ 1978

The current Constitution was approved in 1978. Spaniards voted for it in a referendum on 6 December 1978, and it came into force on 29 December. That is why 6 December is Constitution Day, a national holiday. In 1975 Franco died, and in 1982 the PSOE won the elections: these are important dates, but different ones. The Constitution of 1978 is the longest-lasting one in the history of Spain.