A '''Ship's bells''' are used to indicate time onboard ship. One bell sounds for each half hour. One bell means 12:30, two bells mean 1:00, three bells mean 1:30, and so on until 4:00 ("eight bells"). At 4:30 the cycle begins again with one bell.<ref>U.S. Department of Transportation Maritime Administration [http://www.marad.dot.gov/publications/glossary/glossary.html]</ref>
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A '''Ship's bells''' are used to indicate time onboard ship. One bell sounds for each half hour. Bells are rung in pairs to make it easier to count.<ref>http://www.boatsafe.com/nauticalknowhow/shipbee.htm</ref> Thus, for a watch starting at 12:00, one bell means 12:30, two bells mean 1:00, two bells pause 1 bell means 1:30, and so on until 4:00 ("eight bells"). This cycle starts again for the next watch.
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The use of 30 minutes as the interval between bells originates from the use of a half hour glass to keep time. Each half hour, the glass would be flipped and the appropriate count of the bell would be rung.<ref>http://www.history.navy.mil/faqs/faq83-1.htm</ref>