As a non-reducing biphasic schedule, this E1 provides much flexibility. The nap can be anywhere between ~10 and ~40 minutes. The nap duration can change from day to day, and can start at different times each day if desired. Similarly, the core duration is not fixed and sleepers should rely on natural wakes for it. This scheduling variant can be slightly flexible even in adaptation (it is recommended that the core should not be more flexible than an 2-hour window when first adapting, to keep the circadian rhythm consistent).
