Download the file in this post It will help you lookup the sunrise, sunset time for th longitude you're at.
http://www.subsim.com/radioroom/showthread.php?t=129914
Even today, boats run off a standard time and do not change their clocks as they pass from one time zone to another. Avoids confusion when sending / receiving orders with boats scattered all over the deep blue sea. They will have a seperate clock for local time as a reference, but operational orders are exchanged using the std time.
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"There are only two types of ships- submarines...... and targets"
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"you wouldn't catch me on a ship that deliberately sinks itself"- comment to me from a surface sailor.
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