In pre-modern times, it was relatively easy to determine the end of a fast day. The advent of airplane travel, however, has raised a host of questions as to when the fast should end. In this series, we shall discuss four common scenarios: traveling east and not crossing the international dateline (nightfall arrives earlier), traveling west and not crossing the dateline (nightfall arrives later), traveling west and crossing the dateline (potentially curtailing the fast by many hours or even avoiding the fast altogether), and traveling east and crossing the dateline (possibly encountering the fast day twice).
Traveling East Without Crossing the Dateline
The classic responsum that addresses the question of the impact of the changing time zones on Halachic matters was authored by the Radbaz (Teshuvot 1:76) in the sixteenth century. The Radbaz writes that the end time for Shabbat is determined by the advent of Tzeit HaKochavim (the appearance of three medium sized stars) in the specific place that a person finds himself on Shabbat, even if Shabbat has not yet ended in the individual's usual place of residence (see Seforno to Vayikra 23:3 who adopts a similar approach).
A proof to this approach may be derived from the Gemara (Shabbat 118b) that praises those who begin Shabbat in Tiberius and those who end Shabbat in Tzippori (located in the lower Galilee almost at a midpoint between Haifa and Tiberius). Rashi (ad. loc. s.v. MiMachnisei) explains that Tiberius lies on a low altitude and the sun appears to set early there, so its residents begin Shabbat early. Tzippori, on the other hand, rests on a mountain where the sun appears to set late, and its residents observe Shabbat until quite late (my cousin Meir Rotem, an engineer who resides close to Tzippori, informed me that Tiberius lies 212 meters below sea level and estimates that Tzippori lies between 70 and 100 meters above sea level).
Rav Akiva Eiger (Gilyon HaShas ad. loc.) cites a responsum of the Ri Migash (number 45) who explains that the praise refers specifically to those who begin Shabbat in Tiberius and walk on Shabbat to Tzippori and complete the Shabbat in Tzippori. The Ri Migash clarifies that Tzippori is within the Techum Shabbat (Shabbat boundary in which one is permitted to walk on Shabbat) of Tiberius, and Meir Rotem informs me that one could walk from Tiberius to Tzippori in one day, although it would be a challenging journey since he would be walking uphill. The people who begin Shabbat in Tiberius and end it in Tzippori deserve praise because they place themselves in a situation in which they would be obligated to observe Shabbat longer (in general, Halacha encourages us to create situations where we are obligated to perform a Mitzvah, such as the practice of men to wear a four cornered garment that requires Tzitztit, see Menachot 41a and Tosafot Pesachim 113b s.v. VeEin Lo).
This interpretation of Shabbat 118b seems to teach that even if one is a resident of Tzippori, he must accept Shabbat when it begins in Tiberius, even though it has not yet begun in Tzippori. Similarly, a resident of Tiberius must wait until Tzeit HaKochavim in Tzippori to end Shabbat even though Shabbat has already ended in Tiberius. This seems to conclusively prove the assertion of the Radbaz that the beginning and end of Shabbat is determined by one's location on Shabbat and not by his usual place of residence.
Rav Zvi Pesach Frank (Mikraei Kodesh II:215) questions this proof from the Gemara in Shabbat. He suggests that this passage merely proves that one must be strict in case in which Shabbat ends later than it does in one's hometown, as the Gemara mentions only one who travels from Tiberius to Tzippori. The Gemara does not, however, discuss whether a resident of Tzippori visiting Tiberius may end Shabbat earlier than it ends in Tzippori. It is possible, writes Rav Zvi Pesach, that Halacha requires both that Shabbat end in one's location and his residence. Thus, Rav Frank questions the ruling of the Radbaz (see the comments of the Harerei Kodesh) and remains unsure whether an American who lands in Israel may count the Omer at a time when it is nightfall in Israel but not yet Tzeit HaKochavim in the United States.
Nearly all contemporary Poskim accept the Radbaz's ruling in both a strict and lenient direction. For example, Dayan Weisz (Teshuvot Minchat Yitzchak 6:84), Rav Wosner (Teshuvot Sheivet HaLevi 2:93 and 6:129:26), Rav Ovadia Yosef (Taharat HaBayit 2:277-280) and Rav Feivel Cohen (Badei HaShulchan 196:1, Beiurim s.v. Shivat Yamim) all rule that an individual who begins counting seven clean days in the United States and subsequently travels to Israel may immerse at nightfall in Israel even though it is not yet Tzeit HaKochavim in America. This is a striking example, since Poskim are normally quite strict about the seven clean days (see, for example, Shulchan Aruch Yoreh Deah 196:4 and my Gray Matter 2:98-100), yet they rule in accordance with the Radbaz even in a lenient direction.
These authorities rely to a great extent on an important early twentieth century ruling of Teshuvot Chavatzelet HaSharon (1:Y.D. 47). This great authority adopts the approach of the Radbaz in both a strict and lenient direction, and asserts that it applies to all Halachic concerns. The Chavatzelet HaSharon cites as proof the common practice to regard a boy as Bar Mitzvah immediately at Tzeit HaKochavim on his thirteenth birthday without inquiry as to the location of his birth to determine if it is already Tzeit HaKochavim in that locale.
Accordingly, it is not surprising that Rav Aharon Felder (Moadei Yeshurun page 109) cites Rav Moshe Feinstein's ruling that one who travels east may end the fast when it becomes Tzeit HaKochavim in his location, even though his fasting time will be reduced as a result. Rav Hershel Schachter told me that we should follow this ruling of Rav Moshe. Moreover, Rav Schachter rules that if the plane turns back west after one has reached Tzeit HaKochavim, one is not obligated to continue fasting. We should add that it is not proper to deliberately schedule one's eastbound plane travel for a fast day in order to avoid the obligation to fast, since Halacha wants us to place ourselves into situations of obligation, not avoid them, as we discussed above.
Traveling West without Crossing the Dateline
Those who travel west on a fast day are faced with the opposite problem. Their fast will be lengthened, as they will encounter nightfall much later than they would at home since they are traveling in the same direction as the sun (so to speak). The question is whether westbound travelers must continue their fast until they encounter Tzeit HaKochavim.
The initial question that must be addressed is the status of the obligation to fast on Shiva Asar BeTammuz (when travelers are most interested in not extending this long summer fast), Tzom Gedaliah, and Asarah BeTeiveit (the status of Taanit Esther is addressed in an essay that appears at www.koltorah.org). If it can be determined that we observe these fasts as Minhag (custom) and not rabbinic law, Poskim might suggest an approach to justify ending these fasts earlier. Tisha BeAv, though, undoubtedly constitutes a rabbinic obligation, and one must wait until nightfall to end the fast. Chazal are quite strict about Tisha BeAv (see Rosh HaShanah 18b and Taanit 12b), as they even treat it with the severity of Yom Kippur in some instances (see Pesachim 54b).
The primary source for this discussion is the Gemara (Rosh HaShanah 18b) that asks why the three aforementioned days are described in Zechariah (8:19) on one hand as fast days and on the other hand as days that will eventually be a time of joy. The Gemara cites Rav Papa who resolves this contradiction by distinguishing between three different situations.
When peace prevails, these days will be a time of celebration. Rashi explains this refers to a time when Nochrim do not control us. I sadly recall a comment made by Rav Yosef Dov Soloveitchik in Shiur at Yeshiva University in 1983. He remarked that Israel today is controlled to a great extent by the United States State Department in a manner not very different from the way the Jews were controlled by the Persian Empire during the early Bayit Sheini period. According to this approach, our times cannot be described as a time of peace despite the establishment of Medinat Yisrael.
The Gemara continues that if we suffer from government persecution, the three days will be obligatory days of fasting. Rav Yosef Dov Soloveitchik (cited by Rav Hershel Schachter in Nefesh HaRav p.197) related that there were Gedolim in Europe who ruled that the Holocaust years were times of government persecution and that we were obligated to fast on these three days according to rabbinic law. Rav Schachter clarified (in a personal conversation) that this ruling applied only to those suffering directly under Nazi rule and not those who lived in the United States.
The Gemara concludes that in a time of neither peace nor government persecution, fasting is optional. The Gemara clarifies, however, that one must fast on Tisha BeAv even if there is no government persecution, due to the severity of the tragedies that occurred on that day.
, in our times, when neither peace nor government persecution prevails, there is no rabbinic obligation to fast. However, the Maggid Mishneh (commenting to Rambam Hilchot Taaniot) records that "now" (the time of the Rishonim) the common practice is for everyone to fast on these three fasts even if there is no government persecution. The Maggid Mishneh's assertion is codified as normative Halacha by the Shulchan Aruch (Orach Chaim 549:1 and 550:1) and Mishnah Berurah (550:1). In other words, even though we are not (in most situations) obligated to fast on these three days, the custom adopted during the time of the Rishonim to fast on these days even when there is no government persecution is accepted.
Next week, we shall (IY"H and B"N) explore the possibility of westbound travelers ending a fast before nightfall based on the fact that today it is merely a custom to fast Shiva Asar BeTammuz, Tzom Gedaliah, and Asarah BeTeiveit.