Ordinary Requirement #11 - Time

Requirement 11:

1. Understand Universal coordinated time (Greenwich mean time) and zone time, and demonstrate the ability to convert from one to the other for your local area. Name the seven watches and bell time.
   
   
2. Understand the 24-hour system of telling time.
   
   

Universal Coordinated Time

• Universal Coordinated Time (UTC) is the international time standard.
  
  
• It is the current term for what was commonly referred to as Greenwich Meridian Time (GMT).
  
  
• Zero (0) hours UTC is midnight in Greenwich England, which lies on the zero longitudinal meridian.
  
  
• Universal time is based on a 24 hour clock. Examples:
  
  
• 4 pm UTC is expressed as 16:00 UTC (sixteen hours, zero minutes)
  
  

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Time Zone

• Since a day is 24 hours long, the world may be split into 15 degree wide longitudinal bands (360 degrees/24 hrs).
  
  
• Each band represents one hour.
  
  

• American Time Zones are:
  
  
• Eastern Time Zone (EST) is UTC –5 hours.
  
  
• Central Time Zone (CST) is UTC –6 hours.
  
  
• Mountain Time Zone (MST) is UTC –7 hours.
  
  
• Pacific Time Zone (PST) is UTC –8 hours.
  
  
• Alaska Time Zone (AKST) is UTC –9 hours.
  
  
• Hawaiian Time Zone (HST) is UTC –10 hours.
  
  

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Seven Watches and Bell Time

• When a ship is underway operations stations must be manned 24 hours a day.
  
  
• The ship’s crew is divided into “watches” which rotate being on duty.
  
  
• Being on duty is also called being “on watch”.
  
  
• In the sailing ship era before the development of mechanical clocks the passage of each 4-hour watch was marked with an hourglass which ran 30 minutes.
  
  
• Each half hour, when the glass was turned over, the ship’s bell was struck.
  
  

• A person standing watch could tell by listening to the bells:
  
  
• Where he was in his watch
  
  
• How long it would be before the next watch came on deck
  
  
• What time it was
  
  

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