OK, we've got some discussion going on about issues affecting life within the gray zone of the Halachic Dateline and the International Dateline, but what is the original source of such a concept, if there is one? Can it not just be that whatever is deemed Saturday in some remote place in the world is Saturday (as in the minority opinion at the end of this article)?

  • That's not even the simplest answer. The simplest suggestion is everyone counts seven days from when they were born and does Shabbat then. Doesn't matter what others around you are doing. Seven sunsets, period.
    – Double AA
    Commented Aug 22, 2013 at 6:22
  • @DoubleAA, that might be simple, but it's also ludicrously arbitrary. Can a convert or B"T just choose any random day to start counting?
    – Seth J
    Commented Aug 22, 2013 at 13:25
  • @SethJ; Nobody can just start counting arbitrarily, unless he is stranded far from civilization without technology or any way to know the day. @DoubleAA was just making the point that the simplest theoretical way to calculate when Shabbos is would be by counting 7 days, not by following the local interpretation of Saturday. Commented Jul 21, 2014 at 23:18
  • @SethJ It would not have seemed so odd back before Magellan.
    – Double AA
    Commented Jul 22, 2014 at 1:26
  • @DoubleAA, before Magellan (and before commercial flight), wouldn't a traveler to a remote region continue his counting/dating from where he was yesterday? He would not be traveling vast distances in a matter of a few hours. Granted, he may lose track of his days if he's not paying attention or keeping a journal, but this is a question about the black letter of what is considered a Saturday, not what a loner in the wild should do if he loses track of his days.
    – Seth J
    Commented Jul 22, 2014 at 14:15

1 Answer 1


I'm not sure I understand your question, but basically many rabbis feel that the Torah states where the dateline should be, so we don't really care what the local population thinks. (Though a frustrated Rabbi Yitzchak Zev Brisker, when asked about the dateline, exclaimed -- " I don't know. And I don't know why everyone else thinks they know!")

There are various Talmudic statements that could be read as placing the dateline either 90 or 180 degrees east of Jerusalem. If you feel the Talmud fixes the Halachic dateline, that's what we'd be bound to follow.

From TzemachDovid.org:

Some point to a Gemara in Rosh HaShanah (20b) which indicates that the Beis Din would not declare a day to be Rosh Chodesh unless the new moon was visible in Eretz Yisrael before noon on that day; if it appeared after noon, the next day would be Rosh Chodesh. Although certain Rishonim explain the Gemara (Ibid.) as referring only to details concerning the declaration of Rosh Chodesh, the interpretation of the Ba'al HaMaor (Ibid. 5a in Rif s.v. Ki) and others relates it directly to this issue of the date line. ...

This means that the area 90 degrees east (6 hours ahead) of Yerushalayim was then experiencing nightfall (sunset) and was already beginning the next day. That location, then, must be the date line because that was the first place on earth to go on to the next day; this indeed is where the Baal HaMaor (Ibid.) places the date line, as shown above.

This position about the date line is articulated as well in the Sefer HaKuzari (Maamar 2 Siman 20), and is clearly accepted by the Ran in Rosh HaShanah (Chidushai HaRan to Rosh HaShanah Ibid. s.v. Tzarich), and, apparently, by the Ritva there (Ibid. s.v. Ki).

  • Shalom, that's exactly the type of source I mean. I know the Chazon Ish and others have given various opinions in degrees east and west of Jerusalem, but what I want to know is, on what basis do they stake their opinions?
    – Seth J
    Commented Dec 30, 2011 at 18:14
  • Again, 90 East is based on Baal HaMaor's reading of Rosh Hashanah 20b, has to be noon in Jerusalem. 180 East is based on several things, one of them being the Gemara's calling Jerusalem "the center of the world."
    – Shalom
    Commented Dec 30, 2011 at 20:54

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