The Red Hour marked the beginning of the Festival on Beta III during the governance of Landru. It started at six o'clock in the afternoon.
In 2267, Bilar warned the USS Enterprise landing party searching for Hikaru Sulu and O'Neil to hurry to Reger's house, as the Red Hour was almost upon them.
Later, after they arrived at Reger's place, Hacom noted that the Red Hour had already begun. (TOS: "The Return of the Archons")