9786 —השלכות הלכתיות של חציית קו התאריך הבינלאומי

9 Kislev, 5730.

Shalom u'Vrachah!

Your comment is not entirely clear. It seems you have combined two entirely different cases: regarding the change in counting days for one who is on one side of the date line; for one who crosses from east to west; and for one who crosses from west to east. The discussion in the sichah concerns only the change—by crossing the line—in the order of days in counting, weeks, etc.

There could be another change—by traveling from east to west or vice versa—which shortens or lengthens the measure of time. This requires a special halachic ruling and it is difficult to find sources for it in Shas, etc.—up to what is discussed in Shabbat (118b) about those who bring in Shabbat early in Tiberias and those who end Shabbat late in Tzippori, though this is not exactly comparable. And it is obvious—and especially nowadays—that one could circle the globe several times within a single hour and see multiple sunrises within that hour, but certainly one would not count multiple days or weeks because of these phenomena.

See also the sources cited in Ketzos HaShulchan—Shaarim HaMetzuyanim BaHalacha at the beginning of Hilchos Shabbos, and more.

I will mention you at the Ohel.

Summary

The Rebbe distinguishes between halachic implications of crossing the International Date Line versus merely traveling east or west. Only crossing the date line changes one's calendar count; rapid travel does not multiply days or weeks. Complexities require careful halachic consideration.