Managing 24/7

How Long Have People Been Working Shiftwork?

Shiftworkers have existed since ancient times, among them the watchmen of ancient kingdoms and the military. We can trace modern-day shiftwork to the late 1800s, when the invention of the lightbulb and the increased costs of fixed assets and startup time in steel mills, iron foundries, and textile mills compelled a transition to “nonstop production.”

Initial schedules split the workforce into a day crew and a night crew that typically rotated every two weeks. The first crew would work 13 straight days (12-hour shifts) followed by a continuous 24-hour shift. This exhausting day was immediately followed by 13 straight night shifts, with one day off at the end before starting this work pattern again (Figure 1).

1800 Schedule

Figure 1 - A typical 24/7 schedule used in the late 1800s. (Work column is hours worked; pay column is hours paid if federal overtime laws had existed. Average is average hours worked per week.)

This back-breaking schedule resulted in high rates of workplace accidents and injuries. But with no federal overtime, OSHA requirements, workers' compensation, or third-party liability, employers had little incentive to consider human design limitations when running these 24/7 operations.

Union pressure to limit the workday to eight hours began as early as 1866, culminating in the violent and unsuccessful riots in Haymarket Square, Chicago, in 1886. Little progress was made until 1933, when Congress enacted the National Industrial Recovery Act, which included provisions for minimum wages, maximum work hours, and collective bargaining. This act was soon repealed, but the Wagner Act replaced it.

As part of these new regulations, employers were mandated to pay time-and-a-half in overtime wages for any work in excess of a weekly level of 40 hours. This spurred the change to an eight-hour workday, with the traditional day, evening, and nightshifts becoming commonplace (Figure 2).

1920 Schedule

Figure 2. A common eight-hour, seven-days-a-week schedule used from 1920 onwards. “Rest” days were counted as the 24-hour block between shift transitions (i.e. last day shift, next day off, start working in the evening = 24 hours off)


In the 1960s, the 12-hour shift started to regain popularity, mostly for weekend work, as this allowed workers to enjoy more weekend time off. Some companies adopted 12-hour schedules for all shifts, a trend that continues to increase today due to the extra time off and the longer breaks provided by 12-hour shifts between the work blocks. In an 8-hour shift system, three crews are needed each day, with only one crew gaining time off. In a 12-hour system, two crews are needed while two crews are off work. This results in working 75% of the days on an 8-hour shift system, and 50% of the days in a 12-hour shift system.

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