The Fourth Interval was the period of time in Pernese history that began at the end of the Fourth Pass and ended at the beginning of the Fifth Pass. It spanned the Turns 808AL through 1258AL. It was also known as the First Long Interval.

Unknown to the Pernese at the time, the interval was caused by the explosion of one of the colony ship engines on the Red Star as part of AIVAS' plan to end Threadfall on Pern.

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