If a person takes a flight on Tisha B’Ab from New York to Israel, when does he end his fast – when the fast ends in Israel, or when the fast ends in New York? Israel is seven hours ahead of New York, and thus if he follows Israel Time, he will end up observing Tisha B’Ab for seven fewer hours than he would if he remains in New York. May he end Tisha B’Ab when the observance ends in Israel, or must he wait an additional seven hours, until the fast ends in New York, where he began the observance of Tisha B’Ab?
This question was addressed both by Rav Moshe Feinstein (Russia-New York, 1895-1986) and by Hacham Ovadia Yosef, and both ruled that a traveler ends his observance of Tisha B’Ab when Tisha B’Ab ends in his current location, regardless of when he began the observance. In the case described, the traveler will end Tisha B’Ab when the fast ends in Israel, and he does not have to wait an additional seven hours until Tisha B’Ab ends in New York.
These authorities added that this principle applies to numerous other Halachic contexts, as well. For example, it is very common (Baruch Hashem!!) in our community for families to travel to Israel to celebrate a boy’s Bar Misva. Often, the celebration will take place on the boy’s thirteenth birthday in Israel, even when the birthday has not yet set in back in America. Since the family follows Israel Time, the boy becomes Bar Misva once the date arrives in Israel, even if the date had not yet arrived in the United States.
This applies as well in a case of a couple that travels to Israel for their firstborn son’s Pidyon Ha’ben. They may perform the Pidyon Ha’ben once the thirty-first day sets in according to Israel Time, even though the required duration has not yet passed back in America. Similarly, if a person travels on a cruise and observes Shabbat on the boat, he may end up observing Shabbat for fewer than 24 hours. If the ship is traveling eastward, he may end Shabbat when nightfall occurs wherever he is, even if this occurs early than 24 hours after Shabbat had begun.
It should be noted, however, that this applies in the opposite direction, as well. Thus, for example, if a person travels on Tisha B’Ab from Israel to New York, then he may not end the fast until the time the fast ends in his current location, and he must therefore observe an extra seven hours of fasting.
Summary: If a person travels during Tisha B’Ab to a different time zone, he ends Tisha B’Ab when it ends in his current location. Thus, if one travels from New York to Israel, he will observe seven fewer hours, whereas if he travels from Israel to New York, he will observe seven additional hours. Similarly, a boy who travels from New York to Israel for his Bar Misva officially becomes a Bar Misva when his birthday occurs in Israel, even if the date has not yet arrived back home, and a firstborn boy may have his Pidyon Ha’ben on the thirty-first day in his current location, even if it is still the thirtieth day at the place where he was born.