Since 1991, the average Super Bowl start time has been 6:30 p.m. EST. This is so that the game is played during primetime hours on the East Coast while still finishing before younger viewers need to sleep.
In the Super Bowl era since 1991, the earliest Super Bowl start time was 6:19 p.m. EST in 1991, while the latest start time was 6:40 p.m. EST. Before 1991, the start time fluctuated enough to bring the overall average time earlier. The earliest Super Bowl start time was 2 p.m. EST in 1971; all Super Bowls before 1978 started before 5 p.m. EST.