During how many years did Franklin D. Roosevelt lead the country?

Franklin D. Roosevelt served as President of the United States for an unprecedented four terms, from March 4, 1933, until his death on April 12, 1945. His presidency spanned a total of 12 years, making him the longest-serving president in American history. He was first elected in the midst of the Great Depression and served until the end of World War II, leading the country through significant challenges and transformative periods in history. Roosevelt's time in office fundamentally changed the role of the federal government in American life and set a precedent for future executives. The answer reflects the entirety of his leadership duration accurately, reinforcing the significant impact his presidency had on the nation.