Oscar van Vlijmen <ovv@hetnet.nl> writes:
Bowditch - The American Practical Navigator, Chapter 18 Time, Section 1806 Zone Time; National Imagery And Mapping Agency; 1995.
The 2002 edition of that reference can be found here: http://pollux.nss.nima.mil/pubs/pubs_j_apn_sections.html?rid=187
See also "The International Date Line" at the end of the TZ australasia file.
Thanks. The main disagreement between the American Practical Navigator and the australasia file is that the former mentions only the 180-degree line with respect to time zones on the high seas, whereas the latter mentions the International Date Line. So the two sources disagree for ships sailing in international waters in western-hemisphere Kiribati. I don't know who's "right", but the American Practical Navigator is about as authoritative a reference as I know, so I suspect it closer to being "right" (at least for US ships).