Generally speaking, a Ben Hutz La’aretz – meaning, somebody who lives outside Israel – who visits Israel for Yom Tob must observe two days of Yom Tob just as he does at home. This is very common, and, in fact, there are numerous Minyanim arranged in Israel for visitors from the Diaspora on the second day of Yom Tob.
However, Rav Shelomo Zalman Auerbach (Jerusalem, 1910-1995), in his work Minhat Shelomo (vol. 1, 19:7), makes an important exception to this rule. He writes that if a Ben Hutz La’aretz has a residence in Israel, and he has made it his practice to spend all Shalosh Regalim (Pesah, Shabuot and Sukkot) in Israel each year, then he observes only one day of Yom Tob. Even though he lives outside Israel throughout the rest of the year, he nevertheless has the status of an Israeli resident with respect to Yom Tob. Since the distinction between an Israeli resident and a Diaspora resident in this regard is relevant only on the Shalosh Regalim, and this individual spends all Shalosh Regalim in Israel, he is considered an Israeli resident and thus observes only one day of Yom Tob. This is also the ruling of Hacham Ovadia Yosef, in his work Hazon Ovadia (p. 152; listen to audio recording for precise citation). Recently, some people who always spend the Shalosh Regalim in Israel posed this question to Rav Shelomo Amar, the Sephardic Chief Rabbi of the State of Israel, and he instructed them to follow this ruling and observe only one day of Yom Tob. (They also asked Hacham Ovadia, who, needless to say, followed his ruling in Hazon Ovadia and instructed them to observe just one day.)
Rav Shelomo Zalman Auerbach was asked whether this ruling would apply to somebody who does not own a residence in Israel, but rents a hotel room for all Shalosh Regalim each year. He replied that in this situation, too, a person is considered an Israeli resident and would observe only one day of Yom Tob, since he always spends the Shalosh Regalim in Israel.
Hacham Ben Sion Abba Shaul (Israel, 1923-1998), in his work of responsa (vol. 3, p. 225), disagrees with this ruling of Rav Shelomo Zalman. In his view, a person’s status is determined based upon his primary residence, and therefore even if one always visits Israel for the Shalosh Regalim, he is considered a Ben Hutz La’aretz and must observe two days of Yom Tob, since his primary residence is outside Israel.
In any event, in light of the ruling of the aforementioned Halachic authorities, those who always visit Israel for the Shalosh Regalim observe only one day of Yom Tob, even though generally those who visit Israel from the Diaspora for Yom Tob must observe two days.
Summary: Generally, Diaspora residents who visit Israel for Yom Tob must observe two days of Yom Tob, as they do at home in the Diaspora. However, one who always spends all Shalosh Regalim (Pesah, Shabuot and Sukkot) in Israel observes only one day of Yom Tob, like Israeli residents.
