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    Re: Time Zone Designations
    From: Lu Abel
    Date: 2017 Jan 3, 02:06 +0000
    Part of the +13 vs -13 issue could be what DATE.   If you're just west of the date line your local time is UTC +12 (or zone -12)  

    But then what happens if you want to advance your clock an hour to observe daylight time?  Would that put you in zone +11, the time zone 15 degrees east of you?   That would mean you'd advance your clock by one hour and retard your calendar by one day!!

    Better an imaginary zone -13 and UTC +13.

    In a slightly different vein, one of the local TV stations in the San Francisco area noted that there was a flight that left Shanghai on Jan 1st but landed in SF on Dec 31st.   Departed in 2017 and arrived in 2016! 



    From: David C <NoReply_DavidC@fer3.com>
    To: luabel@ymail.com
    Sent: Monday, January 2, 2017 5:43 PM
    Subject: [NavList] Time Zone Designations

    The subject of time just keeps growing and growing..........
    NZ is in time zone -12 ( Admiralty Manual  of Navigation).
    When NZST is in use zone time is UTC + 12. When NZDT is in use zone time is UTC + 13. Currently NZDT is in use.
    When I have given details of an observation I have given my time as, for example,  13:43:56 (zone -13).  Clearly that is incorrect as there is no zone -13.  Should I give my time as:
    13:43:56 (zone -12, NZDT)
    13:43:56 (UTC + 13)
    13:43:56 (zone -13)  because -13 is added to zone time to get UTC. This is the time zone sign convention.
    or some other format?


       
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