6 thoughts on “The Halachic Date Line Map”

      1. Thank you for pointing me to this article (though you’d mentioned it already and I could have read it on my own). It says:
        “Hawaii would then be nineteen hours ahead of Baltimore, rather than five hours behind” which means that halachically speaking there is no UTC rather halachic offset is from Jerusalem time. Am I understanding this right?

        1. Mordechai,
          I probably misunderstand you. I am not sure you how UTC (or GMT) would play a part here. UTC is about 12 hours from the international date line (IDL). Saying Baltimore is X number of hours from Hawaii has nothing to do with UTC. Even if the Greenwich observatory been in NY and GMT would be the NY timezone, the statement about Hawaii would have been true, since there is nothing really connecting GMT to the international dateline but the fact that they are about 12 hours apart. GMT time was established well before the convention that decided the exact location of the IDL. There is one opinion (mentioned in my post) that the International Date Line is the halachic dateline. but according to most others, the dateline is either 90° (6 hours east of Yerushlayim) or 180° (12 hours) from Yerushalayim.

  1. Thank you so much for this map and explanation. Very useful indeed. I just learned through parts of Rav Yechiel Michel Tucazinsky book “Hayomam B’kadur Ha’aretz.” He specifically mentions (siman 25) that in his opinion the dateline should not go through Alaska (since 1867 when it was bought from Russia by the US) but that the Bering Straight should be the dateline. Maybe you could point that out to Rabbi Heber (your map already reflects this).

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