Passes and Intervals form a fundamental 250-Turn cycle in Pernese history. They are a result of the Red Star's 250-Turn orbit. A Pass is a 50-Turn period during which Thread falls, while the Interval is the period, usually 200 Turns, but in the case of the Long Intervals, 450 Turns, during which Thread does not fall. There have been nine passes and eight intervals so far, and, thanks to the AIVAS' Red Star Diversion Project, the present Pass will be the last one.