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    Re: Time zone sign conventions
    From: Brad Morris
    Date: 2019 Feb 12, 23:03 -0500
    Hi Steve

    Here is how I think of time zones.

    If the fellow I want to speak is east of me, then I must SUBTRACT the zone difference from his zone time to get mine.  Example: David lives in the UK.  It is 2 pm there.  I live in NY.  The zone difference is 5, so my time is 9AM.

    If the fellow I want to speak to is west of me, then i must ADD the zone difference from his time zone to get mine.  Example:  Greg lives in California.  It is 2 PM there.  I live in NY, the zone difference is 3, so my time is 5 pm.

    The sign convention you use is just the direction of the zone difference.  If i wanted to find Greg's time, knowing my own, I would subtract.  If I wanted David's time, knowing my own, I would add.  

    Going east from a known zone, ADD time zone difference.

    Going west from a known zone, SUBTRACT time zone difference.

    Brad

    On Tue, Feb 12, 2019, 8:02 PM Steve E. Bryant <NoReply_Bryant@fer3.com wrote:

    Thank you to Frank, Gary, and Brad for your comments!

    While I am still not able to recall the specific source that originally confused me by clearly referring to western zone descriptions with the minus sign (-) and the eastern time zones with the (+), it seem that they were used by some GPS manufacture’s explanation of a feature utilized by their particular gps I purchased years ago; again I don’t recall for certain.

    However, just recently I discovered a reference in a United States Power Squadrons course manual titled “Electronics Offshore” in which it was stated that the cruise planning tool, - i.e., Visual Passage Planner 2, used in conjunction with a software program titled, CAPN, (the original version of the newer program version identified as OpenCAPN) - uses negative values for western longitudes.  The actual quote is: “Notice in Figure 8-4 that western longitudes are shown as negative values, which is a standard astronomy convention.  This is not a discrepancy, but simply a different convention.”    

    So, for me now, I’m a little more comfortable with trying to stick to processes and procedures that I’ve learned rather than attempting to learn something else altogether different.  I’m at that age when I really do need to focus on Keeping It Simple and staying out of the weeds:  aka “KIS(s)-SOOTW.”  I do thank you for your comments 

    Steve

    PS: I’m still having trouble with the search tool; I’ll try again later. 

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