"the fifth or sixth month..."
See in text (The Masque of the Red Death)
The time jump, which moves the story ahead by “five or six month[s],” approaches the matter of how much time has passed with a degree of imprecision not seen elsewhere. Time governs the progression of the disease and the patterns of the “masked ball,” so the inexact nature of a description like “the fifth or six month” stands out. Prior to entering to castle, mortality and the marking off of each half hour were at the forefront of the public consciousness. However, now that Prospero and his friends have sealed themselves away, the illusion of immunity from the plague has taken hold and they are no longer as diligent about tracking time.