How a 4-on-8-off bill works
Most merchant ships at sea use three watches. Each watch works four hours and then has eight hours off. Over 24 hours that gives two duty periods of four hours each. A common pattern is 0000–0400 and 1200–1600 for one watch, 0400–0800 and 1600–2000 for the next, and 0800–1200 and 2000–2400 for the third. The dog watches of 1600–1800 and 1800–2000 are sometimes used in naval practice to rotate the daily routine.
How this generator works
Enter the start hour of the first watch. The tool builds six four-hour blocks around the clock and assigns them in order to Watch 1, Watch 2 and Watch 3. Rename the watches as 2/O, 3/O and C/O if you want. This is a planning aid only. Rest hours must still meet MLC 2006: at least 10 hours rest in any 24 hours and 77 hours in any 7 days, in not more than two periods.
Who should use it
Useful for chief officers making a watch bill after a crew change. Check the official rest-hours record before the ship sails.