Original: The Royal Rumble in January, WrestleMania in March or April, SummerSlam in August, and Survivor Series in November - were the only annual pay-per-view offerings until 1993, when the WWF started the King of the Ring in June.
Simplified: These four events - the Royal Rumble in January, WrestleMania in March or April, SummerSlam in August, and Survivor Series in November - were the only annual pay-per-view offerings (other than the King of the Ring) from the WWF until 1995.