The shift plan, rota or roster (esp. British) is the central component of a shift schedule in shift work. The schedule includes considerations of shift overlap, shift change times and alignment with the clock, vacation, training, shift differentials, holidays, etc. The shift plan determines the sequence of work (W) and free (F) days within a shift system.
Notation A notation used often identifies day (D), swing (S) and night (N) shifts for the W days and O (off) for rest days.
W work days D day shift, 1st shift, early shift This shift often occurs from either 06:00 or 07:00 to either 14:00 or 15:00 for eight-hour shifts, and from 06:00 to 18:00 for twelve-hour shifts. S swing shift, 2nd shift, late shift, back shift, afternoon shift This shift often occurs from either 14:00 or 15:00 to either 22:00 or 23:00 for eight-hour shifts, and is not used with twelve-hour shifts. N night shift, 3rd shift, graveyard shift This shift often occurs from either 22:00 or 23:00 to either 06:00 or 07:00 for eight-hour shifts, and from 18:00 to 06:00 for twelve-hour shifts. F free days O days off This is defined as a day on which a shift does not begin. A~F work teams (starts from A as first team) Note that a worker transitioning from N to O works for the first six or seven hours of the first day "off". Thus, when days off follow night shifts, the first one or more days "off" are, in fact, days of recovery from lack of nighttime sleep. This daily notation refers to the start of a shift. If a shift starts at 23:00, then this is a W day even though only one hour is worked. The day after this shift is an F day if no shift starts on this day, though many hours have been worked from midnight on. One shift system may allow many shift plans. For example, the twelve-hour, 2nW:2nF system with n = 1 allows twelve different plans in three serially-identical sets. Within a set, DONO has the same sequence as NODO. DNOO is the preferred sequence because days off follow night work and there are two consecutive days off.
3-day shift plans
Prior to 2014, the U.S. Navy used a three shift system with an 18-hour day instead of a 24-hour day. The 24-hour period was divided into four shifts: 00:00-06:00, 06:00-12:00, 12:00-18:00, and 18:00-00:00. A sailor stood watch on their shift. During the off shift there is time to perform maintenance, study for qualifications, and handle collateral duties. During off time the sailor has time to sleep, relax, and perform personal tasks, such as laundry. With sufficient personnel, a given watchstation may benefit from a fourth man (the midnight cowboy or "Balls-to-6"). He would stand the same 6-hour watch in a given 24-hour period, usually from midnight to 06:00 (hence the midnight portion of the name, often shortened to cowboy) and the normal watchstander would then be free. This gave rise to a schedule of six on, twelve off, six on, thirty off, six on, twelve off. Beginning in 2014, the Submarine Force began shifting to a 24-hour day, with watches split into 8 hours on, 16 hours off. This does have the side effect of sailors assigned to a certain shift having the same meals every day, and so the shifts are periodically rotated in order to provide variety. The Surface Fleet began its shift in 2017, transitioning from their "five and dimes" approach of 5 hours on, 10 hours off. This does not apply to the attached air wing, which will work a 12 on, 12 off schedule 7 days a week.
4-day shift plans
In the 12/24/12/48 or 12/24 plan, employees work in shifts of 12 hours; first a "daily shift" (e.g. 07:00 to 18:00), followed by 24 hours' rest, This plan needs four teams for full coverage, and makes an average 42-hour workweek. The pattern repeats in a 4-week cycle, i.e. over 28 days, and has 14 shifts per employee therein.
5-day shift plans
In four on, one off the employee only gets one day off after a work streak of four days. There are 28 shifts per employee in a five-week cycle (i.e. 35 days). This adds up to an average of 42 hours worked per week with 7½-hour shifts. This plan is mainly adopted by industries in which companies prefers to work for all days of the week, often with four (overlapping) shifts per day, and where laws do not let employees work for 12 hours a day for several days. Five groups of employees are needed to cover a specific shift on all days, where each group gets a different day off.
6-day shift plans
In four on, two off the employee gets two days off. There are 28 shifts per employee in a six-week cycle (i.e. 42 days), this adds up to an average of 56 hours worked per week with 12-hour shifts, or 37+1⁄3 hours per week with 8-hour shifts. Three groups are needed for each time span, i.e. to cover the whole day and week a company needs 6 groups for 12-hour shifts or 9 groups for 8-hour shifts. This plan is mainly adopted by industries in which employees do not engage in much physical activity.
Week shift plans
Three-shifts The three-shift system is the most common plan for five 24-hour days per week. The "first shift" often runs from 06:00 to 14:00, "second shift" or "swing shift" from 14:00 to 22:00 and a "third shift" or "night shift" from 22:00 to 06:00, but shifts may also have different length to accommodate for workload, e.g. 7, 8 and 9 or 6, 8 and 10 hours. To provide coverage 24/7, employees have their days off ("weekends") on different days. All of the shifts have desirable and less desirable qualities. First shift has very early starts, so time in the evening before is heavily cut short. The second shift occupies the times during which many people finish work and socialize. The third shift creates a situation in which the employee must sleep during the day; it may be preferred for night owls, for whom this is a desired sleep pattern.
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