As we know, Jews in the Diaspora observe an extra day of Yom Tob which is not observed in Eretz Yisrael. Thus, for example, Shabuot is only one day in Israel, whereas outside Israel it is observed for two days. The observance of the second day – Yom Tob Sheni Shel Galuyot – is required Mi’de’rabbanan (by force of Rabbinic enactment).
The question frequently arises as to whether travelers to Israel must observe the second day of Yom Tob. When a person from America spends Shabuot in Israel, for example, where the second day of Shabuot is an ordinary workday, how must he conduct himself on that day?
The Yalkut Yosef (Yom Tob, p. 381; listen to audio recording for precise citation) rules explicitly that if somebody from the Diaspora is in Israel for Yom Tob, and plans on returning to his home in the Diaspora, then he must observe Yom Tob Sheni. Hacham Ovadia notes that it has become standard practice for Jews visiting Israel to observe Yom Tob Sheni and even to arrange Minyanim on the second day, conducting a full-fledged Yom Tob service, including Torah reading. This has been a common practice for many years, he observes, and no Poskim have objected. And although the Gemara (Pesahim 50) writes that one should follow the religious customs of his current location in order to avoid strife and controversy, Hacham Ovadia ruled that this law does not apply to the case of Yom Tob Sheni in Israel. That law was said regarding visitors who perform activity which is forbidden according to local custom, which could lead to tensions. But people making a Minyan for Yom Tob would not cause any tension and is thus entirely permissible.
If a visitor from the Diaspora mistakenly recited the weekday prayer on Yom Tob Sheni in Israel, he must pray again, reciting the Yom Tob prayers. The only exception is if he added Ya’leh Ve’yabo in the Amida, in which case he has fulfilled his obligation even though he recited a weekday Amida.
If ten men from the Diaspora are not available to make a Minyan on Yom Tob Sheni, the group should pray privately. They cannot count Israeli residents toward a Minyan, since they are not obligated to recite Yom Tob prayers.
A Jew from the Diaspora who is visiting Israel on Yom Tob may ask an Israeli resident to perform Melacha for him on Yom Tob Sheni. Since for Israeli residents the day is an ordinary weekday, the visitor may ask them to perform Melacha, even though he observes that day as Yom Tob. By the same token, if a Jew in the Diaspora owns a factory or other operation in Israel, he may have his Israeli employees work on Yom Tob Sheni, since for them this day is an ordinary weekday.
Summary: People visiting Israel from the Diaspora for Yom Tob must observe Yom Tob Sheni in Israel, and may make Minyanim for the Yom Tob service, though Israeli residents cannot be counted toward the Minyan. In such a case, the visitor may ask an Israeli resident to perform Melacha for him on the second day of Yom Tob.
