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    Is the date ever the same globally?
    From: Jim Thompson
    Date: 2004 Oct 15, 06:37 -0300

    I need to check my understanding of this with the list.  Is this line from a
    book correct:
    "...at the instant of GMT 1200, the date is the same all over the world"?  I
    think it is wrong.
    1. On
    I tried last year to prove that statement to myself, but was unable to do
    so.  See
    Note in that table (I made up this table, so I hope it is right) that when
    it is 1200 at Greenwich on day 10 (say), it is is 2400 the previous day in
    Time Zone Y (ZD -12), and so it can never be the same date at every place on
    the planet at once.  The instant it turns to 1200 at Greenwich, the time in
    M is 2400 on the same day, but the time Y is 2400 on the previous day
    2. There are 25 time zones, not 24, right?  The way I see it, that is
    because the 15d span of longitude around the IDL is divided into Y (ZD -12)
    and M (ZD +12).  Although time is always the same in those two "half zones",
    date is always different.  Am I right?  Or is that just splitting hairs to
    say that there are 25 time zones, since the time in Y and M is always the
    same, even though the date is different?
    (I am working on a CN PowerPoint presentation for teaching, so need to pin
    this down.)
    Jim Thompson
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