Rank by Age(oldest first) ChronologicalRank President Age at Inauguration1. 47 Donald J. Trump 78 years 220 days 2. 46 Joe Biden 78 years 61 days 3. 45 Donald J. Trump 70 years 220 days 4. 40 Ronald Reagan 69 years 348 days 5. 9 William Henry Harrison 68 years 23 days 6. 15 James Buchanan 65 years 315 days 7. 41 George H. W. Bush 64 years 222 days 8. 12 Zachary Taylor 64 years 100 days 9. 34 Dwight D. Eisenhower 62 years 98 days 10. 7 Andrew Jackson 61 years 354 days 11. 2 John Adams 61 years 125 days 12. 38 Gerald R. Ford 61 years 26…