Some factories run processes that are very expensive to shut down, meaning that they must run them continuously. Obviously, this means that there must be workers there all the time as well. A work schedule one sometimes sees at plants that run this way is the rotating shift schedule. One summer I worked at a nylon fiber plant with a schedule like this.

The first thing you do is take your workforce and divide them into four "shifts" or "teams": A, B, C, and D. Then divide the day into three workdays. Where I worked, first shift was from 8 AM to 4 PM, second was from 4 to midnight, and third was from midnight to 8 AM. You work seven days on one shift, get two days off, work seven more days on the next shift, get two more days off, work seven more days on the next shift, and get three days off for a long weekend. Then you do it again. During any given 28-day period, the people on any given shift will be working for 21 days and not working for seven, which is only one more day of work than a normal schedule. There were holidays for which the factory shut down. The only one I was there for was the three day break for Independence Day.

The schedule ends up looking like this:

```day first second third
___ _____ ______ _____
1    A      C     B
A      C     B
A      D     B
A      D     B
A      D     C
A      D     C
7    A      D     C
B      D     C
B      D     C
B      A     C
B      A     C
B      A     D
B      A     D
14    B      A     D
C      A     D
C      A     D
C      B     D
C      B     D
C      B     A
C      B     A
21    C      B     A
D      B     A
D      B     A
D      C     A
D      C     A
D      C     B
D      C     B
D      C     B
```

I would try to adjust my sleep schedule by about an hour every night so that when I had to work the next shift, my body would be ready.