When Jewish laws were first being debated and discussed, the spherical nature of the Earth was not on many rabbis’ minds. And crossing the Pacific? Even less so. But in the last few centuries, and especially in the last few decades, these questions have become more important.
First of all, where is the International Dateline according to Jewish Law? And more practically, if you time things correctly, can you skip the Jewish Sabbath? One need never worry about rolling on Shabbos ever again!
Enter the vast compendium of Jewish Law. And of course, there are many opinions of where the International Dateline falls (the above map is a visualization of these opinions). Here’s a sampling of the discussion:
Therefore, the halachic Dateline of the Chazon Ish avoids going through land by gerrymandering along the Russian and Korean coasts, then along the 125.2°E longitude line, through the East China Sea, Philippine Sea, and Indonesia. Finally, the line cuts eastward, around most of the Australian coast, and south towards Antarctica. According to the Chazon Ish, Japan, New Zealand, and Fiji are on the same side of the Dateline as the United States. When the Japanese and New Zealand residents say it is Saturday, halacha says it is Friday. When they say it is Sunday, it is halachically Shabbos.
Rav Yechiel Michel Tucazinsky, the author of the Gesher Hachaim, in Sefer Hayoman B’Kadur Ha’aretz, bases his ruling on Chazal’s Judaic principle that Yerushalayim is “the center of the world.” If so, the Earth “starts and ends” (i.e. the dateline) on the exact opposite side of the Earth, halfway around the globe at 144.8°W (line E). This line runs from the Gulf of Alaska through the Pacific Ocean east of Hawaii, placing Hawaii on the “other side of the Dateline” from the United States. Hawaii would then be nineteen hours ahead of Baltimore, rather than five hours behind, as it is on the same side of the Dateline as Asia. The day Hawaiians call Friday is halachically Shabbos, and the day they call Saturday is halachically Sunday.
It turns out that in the end, most opinions follow common sense (in general, whatever day the locals say it is, Jewish Law agrees), but it is quite intriguing to see how this conclusion is arrived at.