At Turner Field, the 45-year old Julio Franco hits a home run with the bases loaded in the 1st inning, to became the oldest player in major league history to hit a grand slam as the Braves beat the Phillies, 8 – 4.

On June 3, 2004 — At Turner Field, the 45-year old Julio Franco hits a home run with the bases loaded in the 1st inning, to became the oldest player in major league history to hit a grand slam as the Braves beat the Phillies, 8 – 4.

Source
Baseball Reference June 3