King Juan Carlos I of Spain was born on January 5, 1938. He became the King of Spain in 1975 after the death of dictator Francisco Franco. His reign is noted for the transition of Spain from a dictatorship to a parliamentary democracy, which included the establishment of a new constitution in 1978. Juan Carlos I played a crucial role in modernizing Spain and promoting democratic values. However, his later years were marred by scandals, leading to his abdication in June 2014 in favor of his son, King Felipe VI.