28-hour day

The 28-hour day is a semi-serious concept of personal time management where an organization or individual lives by a 28-hour long schedule with exactly six such cycles within a standard 7-day week of 168 hours, since 6 × 28 = 7 × 24. It was made popular in an issue of the XKCD comic by Randall Munroe.

The plan suggests a sleep cycle of 19 to 20 hours awake followed by 8 to 9 hours asleep: 20/8 or 19/9.

For people who do not need more but less hours per sleeping cycle, the 21-hour day would be an alternative with eight cycles per week since 8 × 21 = 168 as well.

Overview of 21-, 24- and 28-hour days within a standard week

Weekday	Monday																								Tuesday																								Wednesday																								Thursday																								Friday																								Saturday																								Sunday
Hour	00	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15	16	17	18	19	20	21	22	23	00	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15	16	17	18	19	20	21	22	23	00	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15	16	17	18	19	20	21	22	23	00	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15	16	17	18	19	20	21	22	23	00	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15	16	17	18	19	20	21	22	23	00	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15	16	17	18	19	20	21	22	23	00	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15	16	17	18	19	20	21	22	23
Nominal light	darkness						daylight												darkness												daylight												darkness												daylight												darkness												daylight												darkness												daylight												darkness												daylight												darkness												daylight												darkness
16:8	asleep						awake																asleep								awake																asleep								awake																asleep								awake																asleep								awake																asleep								awake																asleep								awake																asleep
20:8	awake														asleep								awake																				asleep								awake																				asleep								awake																				asleep								awake																				asleep								awake																				asleep								awake
19:9	awake														asleep									awake																			asleep									awake																			asleep									awake																			asleep									awake																			asleep									awake																			asleep									awake
15:6	awake				asleep						awake															asleep						awake															asleep						awake															asleep						awake															asleep						awake															asleep						awake															asleep						awake

See also

• Shift Calendar