International date line

Law, Gwil Jr. Gwil_Law at
Mon Jan 3 15:10:40 UTC 2000

> Does anybody know the exact geographical coordinates of the international
> date line?

The International Date Line is not defined by any international standard,
convention, or treaty.  Mapmakers are free to draw it as they please.
Reputable mapmakers will simply ensure that every point of land appears on
the correct side of the IDL, according to the date legally observed there.

When Kiribati adopted a uniform date in 1995, thereby moving the Phoenix and
Line Islands to the west side of the IDL (or, if you prefer, moving the IDL
to the east side of the Phoenix and Line Islands), I suppose that most
mapmakers redrew the IDL following the boundary of Kiribati.  Even that line
has a rather arbitrary nature.  The straight-line boundaries between Pacific
island nations that are shown on many maps are based on an international
convention, but are not legally binding national borders.

An Anglo-French Conference on Time-Keeping at Sea (June, 1917) agreed that
legal time on the high seas would be zone time, i.e., the standard time at
the nearest meridian that is a multiple of fifteen degrees.  The date is
governed by the IDL; therefore, even on the high seas, there may be some
places as late as fourteen hours later than UTC.  And, since the IDL is not
an international standard, there are some places on the high seas where the
correct date is ambiguous.

This information is the best I could find when I was studying the question
a few years ago.  If any of the readers of this list have anything more
authoritative, I would welcome corrections.

Gwillim Law

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