The first watch is from 20.00 until midnight; the middle watch is from midnight to 04.00; the morning watch is from 04.00 until 08.00; the forenoon watch is from 08.00 until noon; the afternoon watch is from noon to 16.00. The next two watches are divided into ‘dog watches’ – the first dog watch is from 16.00 until 18.00 and the last dog watch is from 18.00 until 20.00. The dog watches divide the 24 hour working day into an uneven number of watches so that the watch keepers do not keep the same watches everyday.
The “bells” struck by a ship’s clock are used to “mark the watch,” a ship’s working shift of 4 hours’ duration. The day begins at 1 minute after midnight, and the bell strikes every half hour of the watch: half an hour after midnight is one bell, 1 a.m. is two bells, 1:30 a.m. is three bells and so on until 4 a.m., which is eight bells and the end of the watch. Historically, one member of the crew was to “make rounds” of the ship every half-hour and strike the ship’s bell to let the watch officer know that all was well about the vessel. After the first half-hour of the watch, when one bell was struck, the bells were sounded in groups of two, so that three bells, would be “ding-ding, ding” and four bells would be “ding-ding, ding-ding.”