Changes

Dark period is a way for sleepers to stabilise their circadian rhythms in the absence of long blocks of sleep and increase the quality of SWS. For most schedules, it should start 1.5-3 hours before the dusk (SWS peak) sleep block and continue for around 8 to 12 hours afterwards.

Dark period is a way for sleepers to stabilize their circadian rhythms in the absence of long blocks of sleep and increase the quality of SWS. For most schedules, it should start 1.5-3 hours before the dusk (SWS peak) sleep block and continue for around 8 to 12 hours afterwards.

== Rationale ==

== Rationale ==

Before the advent of electrical lighting in modern times, humans historically had a stable time during the night in which there is little light. This helped stabilise their circadian rhythms and kept them synced to the natural day/night cycle.

Before the advent of electrical lighting in modern times, humans historically had a stable time during the night in which there is little light. This helped stabilize their circadian rhythms and kept them synced to the natural day/night cycle.

Modern humans often use electric lighting during the night. This can cause difficulty sleeping, as the body thinks it is still daytime even if it is already midnight, and is the reason why people often experience the desire to sleep later and later each day. For monophasic sleepers, a somewhat short dark period can be maintained during their sleep hours, which keeps their circadian rhythms relatively stable.

Modern humans often use electric lighting during the night. This can cause difficulty sleeping, as the body thinks it is still daytime even if it is already midnight, and is the reason why people often experience the desire to sleep later and later each day. For monophasic sleepers, a somewhat short dark period can be maintained during their sleep hours, which keeps their circadian rhythms relatively stable.