I believe that all the concert footage was filmed on October 29, 1964, meaning that the 50th anniversary is today. But it's fun to watch any time.
There are 12 headline acts, of which 7 are now in the Rock 'n' Roll Hall of Fame. The film is particularly famous for James Brown's performance (especially his dancing); his spot starts at about 1:17:08. But the whole film - the performers, the dancers (including a young Teri Garr), the screaming teenagers - is a window into a vanished time.