On the Edge: The International Date Line in Halacha

An Overview of a Shiur by Rav Yosef Greenwald for Parshas Tazria/Parshas HaChodesh

(החודש הזה לכם ראש חדשים (שמות יב:א

Where is the Date Line located according to halacha? Three
basic approaches are offered. 

• Chazon
  Ish   
  • 6 hours (90 degrees) ahead
    of Yerushalayim, which runs through Siberia, part of China, and part of
    Australia (though land masses are not divided in his opinion).
  • Based on the Baal HaMaor (to Rosh Hashana) concerning kiddush hachodesh.
  •  Shabbos in Japan is observed on
    Sunday.

• Rav
  Tuchachinsky –
  • 12 hours (180 degrees)
    ahead of Yerushalayim, which runs through part of Alaska and the Pacific Ocean
    to the left of Hawaii.
  • Based on the idea that
    Yerushalayim is the center of the world
  • Shabbos in Hawaii is
    observed on Friday.

• Rav Tzvi
  Pesach Frank/Rav Ovadia Yosef –
  • We follow the regular International
    Date Line.
  • Since the Gemara doesn’t
    address directly, we should follow the local custom.

• Practical Halacha Today
  • Most poskim do not take a definitive stand on the issue.
  • Therefore, many poskim suggest for Shabbos to keep Shabbos on the local
    Saturday and be machmir for melacha deoraisa on the other day.