Understanding the Halachic Date Line and Sefirat Ha'omer

Dear Rabbi, I am a businessman based in Las Vegas, and I am scheduled to travel to Sydney next week. Due to crossing the International Date Line, I anticipate that I will be skipping a day. In light of this, I seek your guidance regarding the counting of the Omer (Sefirat HaOmer). Should I continue counting in accordance with the local practice in Sydney upon my arrival, or is there an alternative method I should follow due to the day I will miss? Thank you very much for your assistance. Kind regards

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Thank you for your question. I would first like to enlighten you that it is interesting to note that according to Jewish Halacha, there is a date line, but it is not the universally accepted Greenwich Mean Time. Rather, it is determined by various sources from the Talmud.

The Chazon Ish writes, based on the Gemara in Rosh Hashanah (page 20b) and the interpretation of the Ba’al HaMa’or, that the date line is positioned 90 degrees east of Jerusalem. This means that when the day begins at the date line, it actually starts six hours later in Jerusalem.

The Chazon Ish explains that if the international date line intersects a landmass, the territory is not split into different date zones. Instead, the date line is adjusted eastward so that the entire nation follows the time zone west of the date line. For example, although the date line might theoretically bisect Australia, it is actually routed to circle around Australia, skirting along the coast near Sydney. Here is a map from Star-K: Star-K International Date Line Map

This leads to a unique halachic implication: if one flies from Sydney and heads west, the aircraft initially travels briefly over the ocean before turning back west. During this time, if it's Sunday in Sydney but the flight crosses the date line, it becomes Shabbat. Consequently, while over the ocean and crossing the date line, it is considered Shabbat, and one should abstain from activities classified as melachot (work forbidden on Shabbat) until the plane returns to flying west, back over the date line.

However, Rav Y. M. Tukatzinsky argues with this and says that Jerusalem is considered "Tabur HaAretz," the center of the world, as described in Yechezkel chapter 38 verse 12, and therefore the date line should be positioned 180 degrees from Jerusalem.

This debate became particularly relevant during World War II when the Mir Yeshiva fled to Kobe, Japan via Siberia on the Trans-Siberian Railway, where they stayed for about nine months. Kobe is located 100 degrees east of Israel (135 degrees east of Greenwich). A dispute arose over the position of the Jewish date line. Some believed it should be 90 degrees from Jerusalem, which would place the Sabbath in Kobe when it was already Sunday in Israel, as Kobe would be beyond the Jewish date line, transitioning to the next day. Others held that it should be 180 degrees from Israel, aligning the Sabbath in Japan with the same day in Israel but six hours earlier.

The controversy extended to the observance of Yom Kippur. There was significant debate about whether to observe it on Wednesday, in line with Jerusalem, or on Thursday. The Chazon Ish famously intervened by sending a telegram that stated: "Dear brothers, eat on Wednesday and observe the Yom Kippur fast on Thursday, and pay no heed to anything else."

Nevertheless, the journey you're planning crosses all the halachic date lines we've discussed, and as a result, you'll essentially be skipping a day. For example, if you leave America on the 21st day of the Omer, you'll arrive on the 23rd day—what happens to the 22nd day? According to the Shulchan Aruch, Orach Chaim, Section 489, Paragraph 8: "If one forgets to recite the blessing on one of the days, whether the first day or any other day, he should continue counting on the subsequent days without a blessing." There are opinions, like that of Rav Hai Gaon, that suggest it is sufficient to count the weeks; however, there are opinions that one needs to count each day, and so missing a day means you cannot continue with a blessing. Therefore, by missing a day of counting due to your flight, you should not continue with a blessing. Instead, as the Mishnah Berurah writes in Se’if 38, you should intend to fulfill your obligation through the blessing recited by the prayer leader (shaliach tzibbur), and in this way continue to count like the destination you are now in.

If, however, one were to fly in the opposite direction, for example from Australia to America, he will be repeating the same count—for example, if in Australia it was the 33rd day of the Omer, he will arrive in America and it will again be the 33rd day of the Omer. In this case, one should count without a beracha just on this extra 33rd day, then the next day continue to count with a bracha as usual.

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• Talmud, Gemara Rosh Hashanah (page 20b)
• Chazon Ish
• Star-K International Date Line Map Link
• Shulchan Aruch, Orach Chaim, Section 489, Se’if 8
• Mishnah Berurah ibid