The watch system adopted in the engine room is usually
a four-hour period on duty followed by eight-hour rest. The word “watch” means
both the period and the crew working at that time. The three watches in any 12
hour period are usually: 12 to 4, 4 to 8, 8 to 12. Thus, for instance, an
engineer on duty for the 8 to 12 watch works from 8 a.m. to 12 noon and from 8
p.m. to 12 midnight.