Watch system

A watch system, watch schedule, or watch bill is a method of assigning regular periods of work duty aboard ships and some other areas of employment. A watch system allows the ship's crew to effectively operate the ship 24 hours a day for the duration of long voyages or operations.

Many watch systems incorporate the concept of dogging, whereby one watch is split into two shorter watches so that there is an odd number each day. Doing so allows crew members to have a different watch schedule each day. Often, the dog watches are set at dinner time to allow the entire crew to be fed in short order.

Traditional system
In the traditional Royal Navy watch system, 'watch' refers to a period of time and to a grouping of personnel. Those members of the crew whose work must be done at all times of the day - known as 'watch-keepers' - are assigned to one of two watches: the Starboard or the Port watch. These can be further divided into two parts, e.g. First Port, Second Starboard. These two watches - or more usually the four parts of watches - alternate in working the following watches:


 * First watch: 2000 to 0000
 * Middle watch: 0000 to 0400
 * Morning watch: 0400 to 0800
 * Forenoon watch: 0800 to 1200
 * Afternoon watch: 1200 to 1600
 * First dog watch: 1600 to 1800
 * Last dog watch: 1800 to 2000

The Royal Navy traditional submarine three watch system is 2 on 4 off during the day (8 a.m. to 8 p.m.) and 3 on 6 off during the night (8 p.m. to 8 a.m.).

Traditional system with three sections
The same arrangement of watch times can also be used with a crew divided into three sections. This gives each sailor more time off-duty, sometimes allowing sleeping periods of over seven hours. Names for the three watches—instead of Port and Starboard—vary from ship to ship. Naming schemes such as "Foremast", "Mainmast" and "Mizzen" and "Red", "White" and "Blue" are common.

Five and dime
The so-called "five-and-dime" arrangement splits the day into five-hour watches, with the exception of a four-hour watch from 22:00 to 02:00.

US Submarine System with three sections
Aboard United States submarines, where the working day is 18 hours instead of 24, the crew is normally divided into three sections, with each section standing 6 hours of watch followed by 12 hours off-watch. The 12 hours off-watch are further divided into the first 6 hours being used for maintenance, cleaning, and entertainment; while the second 6 hours are usually for sleeping.

Note that this arrangement results in one of the sections having two watches in one (24-hour) day, and there are no dog watches. Also, watch reliefs occur no later than the bottom of the hour (2330, 0530, 1130, 1730). This is because the first 30 minutes of the hour are used for the oncoming section to eat, and the second 30 minutes of the hour are used for the off-going section to eat.

One-in-Two Watch System
Some warships now use the one-in-two system, also known as 7s and 5s, for the duration of the watches. This gives the sailors a longer sleeping period than the traditional two-watch system, while still maintaining the ability for the ship to function. Meals are generally scheduled around the watch turnovers at 0700, 1200, and 1700; sometimes a light midnight meal is provided for the 0000 turnover.