Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    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.


    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 


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

    View and reply to this message

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site