Biphasic sleep schedules have been prevalent through time. In a way or another, humans tend to sleep twice a day. There are two types of biphasic patterns; one has a daytime nap of some sort, while the other has 2 concentrated sleep blocks at night. Moreover, there are documents on a lot of famous biphasic sleepers in the modern era. 

  • Segmented sleep was practiced in the northern regions during medieval times.
  • Siesta was popular near the equator.

Overall, schedules in the Biphasic family of sleep schedules typically consist of only two sleep blocks. The main biphasic sleep schedules are Segmented, Siesta and Biphasic-X. Interestingly, they have been the main sleep schedules for a long time throughout human history in some way. Needless to say, they continue to work very well in the modern world.

  • Sleeping in a biphasic style could be more natural than sleeping monophasically; this is because the bodily rhythms naturally tend to lean towards biphasic sleep when there is no artificial light1.
  • Segmented sleep was common throughout the year in preindustrial Europe.
  • Even in “Siesta” cultures, seasonal changes to napping patterns were only minimal.
  • Biphasic sleep was not unique to Western people. People often slept in two segments all over the world2.
  • Sleeping in a Segmented pattern even happens naturally in today’s world; for example, current agricultural societies without electricity tend to sleep in two segments, as well as possibly take naps3.
  • Biphasic-X is a non-reducing biphasic schedule, where sleep reduction is absent. Thus, it is not advisable to attempt to reduce sleep on this schedule because of its high flexibility. 

Segmented (7 hours)

  • Invented by: N/A, historically used by humans.
  • Total sleep: 7 hours.
  • Classification: Biphasic schedule in a Dual Core style.
  • Specification: 2 core sleeps, with a short gap between them.
  • Mechanism: Two sleeps per day, with one sleep in the first half of the night that gives mostly SWS. In addition, another sleep in the second half of the night gives mostly REM. There is usually a 3-hour wake between 2 cores to trigger sleep stage division within them.
  • Adaptation difficulty: Moderate.
  • Ideal scheduling: 1 core around 21:00, should not be later than 22:00ish, 1 core till morning.

Siesta (6 hrs 30 mins)

  • Invented by: N/A, historically used by humans.
  • Total sleep: 6 hours 30 minutes.
  • Classification: Biphasic schedule.
  • Specification: 1 long core + 1 short core, placed roughly opposite each other.
  • Mechanism: Two sleeps per day. The core occupies most of the night. In addition, there is a long sleep block around noon.
  • Adaptation difficulty: Moderate.
  • Ideal scheduling: Core around midnight, siesta at noon.

Everyman 1 (6 hrs 20 minutes)

  • Invented by: Puredoxyk
  • Alternatively known as: Biphasic, E6
  • Total sleep: 6 hours 20 minutes
  • Classification: Biphasic schedule in an Everyman style
  • Specification: 1 long core sleep, 1 short nap
  • Mechanism: Two sleeps per day, main sleep through graveyard hours and a brief rest around noon. However, the core sleep resembles monophasic sleep the most.
  • Adaptation difficulty: Moderate
  • Ideal scheduling: Core at midnight, nap around noon

Biphasic-X (7-9 hours)

  • Invented by: GeneralNguyen
  • Alternatively known as: Prototype X, Experimental X, Bi-x
  • Total sleep: 7-9 hours (equivalent to monophasic baseline)
  • Classification: Flexible, Biphasic, Non-reducing Polyphasic Sleep
  • Specification: 1 long core sleep, naps with varying lengths or consistent length depending on days. The nap contains primarily NREM1/NREM2 with short duration (< ~25-30m) and SWS/REM with longer duration (> 60m).
  • Mechanism: 1 core sleep, 1 nap as main form. More than 1 core sleep or 1 nap (reduce total sleep) is permissible on busier days. However, one should recover afterwards to recover from sleep deprivation. They can increase total sleep by extending either core length or nap length in Biphasic form to keep up napping habits. Both core sleep and nap(s) are flexible; they can move around to a degree to preserve the circadian rhythm.
  • Adaptation difficulty: Easy
  • Ideal scheduling: Consistent dark period everyday, core sleep starts 1-2 hours after dark period. Nap during daytime, no later than 6 PM.

Comparison between Biphasic schedules


  • The assessment table showcases differences between Biphasic schedules, based on standard scheduling.
  • Unless specified otherwise, there will be no mentions of extended versions.
  • The table does not account for short sleepers; thus, these utility criteria will likely vary in them. 
  • Assessment denotations: 
  1. 4/4: Positive, very high viability, or very easy
  2. 3/4: Somewhat decent viability, above average, or somewhat easy
  3. 2/4: Neutral, medium viability
  4. 1/4: Negative, low viability, below average, or overall difficult
Time zone travel (> 5h)
Evening social time (18:00-23:00)
Daytime napping (7:30-17:00)N/A
Nap around meal timeN/A
Overall flexibility
Flexible core
Hidden potentialFirst core can start later (~23:00)Day core can be late (after 17:00)6.5h coreSegmented sleep is possible some days
Time zone travel (> 5h)
Evening social time (18:00-23:00)
Daytime napping (7:30-17:00)N/A
Nap around meal timeN/A
Overall flexibility
Flexible core
Hidden potentialFirst core can start later (~23:00)Day core can be late (after 17:00)
Time zone travel (> 5h)
Evening social time (18:00-23:00)
Daytime napping (7:30-17:00)
Schedule nap around meal time
Overall flexibility
Flexible core
Hidden potential(s)6.5h coreSegmented sleep is possible some days

Brief analysis 

There is no best Biphasic schedule; each one provides different pros and cons that suit specific lifestyles. Therefore, what may apply to a lifestyle does not mean it will apply to others. Additionally, the table only serves to roughly sketch out the potential utilities each schedule provides.

  • Biphasic-X is the schedule with the design to fit all things. It has the highest flexibility of scheduling out of all biphasic schedules. However, it does not offer any sleep reduction from personal monophasic baseline. 
  • Segmented sleep is the only polyphasic schedule that has a 12+ hours wake period in the day. 
  • Regular exercising and occasional caffeine consumption on reducing biphasic schedules (especially extended versions) are overall acceptable. Nonetheless, a Segmented sleeper should only consume caffeine after the second core. 
  • Scheduling sleeps to fit into personal travelling iteration (> 5h time zone difference) is usually difficult for almost all polyphasic schedules. Nevertheless, E1 has the best shot because the 20m nap is easy to fit in. On the other hand, Segmented sleep will likely have to abandon dark period practice. 
  • In the long run, E1 has more napping viability than Siesta because of the easiness to schedule a 20m nap compared to a 90m core.
  • Both E1 and Siesta are better options for evening social time than Segmented. 
  • All Biphasic schedules are flexible if extended. However, the standard versions require more attention when a core is flexed. 

Conclusively, Biphasic schedules are the most popular sleep patterns because it is easy to schedule two sleep blocks per day. The decently high total sleep is also suitable for teenagers and people with high sleep requirements. These schedules are the simplest forms of napping to prepare for more advanced polyphasic schedules. 

Main author: Crimson & GeneralNguyen

Page last updated: 3 March 2021


  1. WEHR, THOMAS A. “In Short Photoperiods, Human Sleep Is Biphasic.” Journal of Sleep Research, vol. 1, no. 2, June 1992, pp. 103-107, 10.1111/j.1365-2869.1992.tb00019.x. [PubMed]
  2. Ekirch, A. Roger. “Sleep in western culture: A historical perspective.” Sleep, Health, and Society: From Aetiology to Public Health (2018): 163.
  3. Claustrat, B. “L’évolution Du Rythme Veille-Sommeil Au Cours de l’Histoire de l’Humanité. Influence de La Lumière Artificielle.” Médecine Du Sommeil, vol. 11, no. 2, Apr. 2014, pp. 68–73, 10.1016/j.msom.2013.09.002.