Rabbi Herschel Schachter
Regarding the Second Day Yom Tov for Visitors in Eretz Yisroel
In Eretz Yisroel the yomim tovim are observed for only one day as proscribed by the Torah. Outside of Eretz Yisroel the rabbis of the Talmud here instituted the second day yom tov, not withstanding the fact that we already have a fixed calendar, and there is no longer any doubt regarding the correct identity of the day of yom tov .
For one from chutz laaretz who is only visiting Eretz Yisroel for yom tov it is well known that there is a difference of opinion among the poskim as to how many days of yom tov one must observe. The majority opinion always was that visitors observe two days . Even if one always visits Eretz Yisroel for Pesach and Succos, but not for Shavuos, R. Shlomo Zalman Auerbach pointed out, based on the gemara, that one must observe two days of yom tov even for Pesach and Succos. The minority view of the Chochom Tzvi (18th century) was that even the visitors in Eretz Yisroel only observe one day. In recent years, this opinion of the Chochom Tzvi has gained more popularity among the poskim .
Then there are compromise opinions. Many observe what has come to be known as "a day and a half." They basically follow the Chochom Tzvi: davening tefillat chol on the second day, putting on tefillin with a bracha, but by way of compromise, they do not do any melacha on the second day to be choshesh for the other opinions. This is what Rav Soloveichik used to advise talmidim. He mentioned that his family tradition was that basically the Chochom Tzvi's opinion was more correct. (On some occasions he would even suggest that the idea of observing issur melacha on the second day might not merely be by way of compromise, but possibly based on pure halacha).
Others have adopted an opposite style of compromise which some humorously refer to as "two and a half days." They follow what was always the majority opinion and observe two days of yom tov, abstaining from melacha on the second day and davening tefillat yom tov including the reciting of kiddush and observing the second seder; but at the same time being choshesh for the opposing view and putting on tefillin the second day without a bracha and listening to havdalah in shul at the end of the first day. (On the several rare occasions that I was visiting in Eretz Yisroel for yom tov this was indeed my personal practice and that of my family.) The rationale behind this practice is not to always be on the lookout for every possible chumra under the sun as some unlearned individuals have incorrectly understood; but rather to follow the classical majority view that visitors must observe two days and at the same time be tolerant enough to show respect for the minority view .
If one is in the practice of always following the views of Rav Soloveitchik, then of course this issue should be no exception and one should observe the "one and a half" days. But, in all honesty there are not many people who actually follow all of the Rav's opinions- considering that he had many many unconventional chumros! If one is a "chochom shehigia lehoraah", then he is entitled and indeed obligated to research each and every halachic issue and to follow his own personal view on any matter. But, if one is not higia lehoraah (as the overwhelming majority of people who learned in yeshiva would be classified) then one may not pick and chose arbitrarily from amongst the various opinions of the poskim. One must either always follow one posek (as the mishna in Avos tells us) or follow the consensus from among the group of poskim he looks up to as his rebeim (because of the fact that that group left an impression on him).
Before this past Peach I was consulted regarding two interesting cases. In the first case, a family was visiting Eretz Yisroel for yom tov. The daughter, a student at Columbia, had previously studied in one of the seminaries in Eretz Yisroel after high school, and was taught there - in accordance with the classical traditional view - that one visiting Eretz Yisroel must observe two days of yom tov. Just a few months before Pesach the father had asked his local Orthodox musmach from down the block, to whom he asks all of his shailas as well, (who happens not to be a practicing pulpit rabbi) and was told that this family should only observe one day of yom tov. The question posed was, does it make sense that half of the family observe one day yom tov and the other half two days. My thoughts on the matter were as follows: the Talmud records that there were many disputes between Beis Hillel and Beis Shammai. Whoever was a follower of Beis Shammai had to abide by their opinions, and whoever was a follower of Beis Hillel had to abide by their opinions. But this is only provided they are together with their own group. If one from Beis Hillel was with a group of followers of Beis Shammai, he was not allowed to follow the views of Beis Hillel, as this would be a violation of lo tisgodedu, causing it to appear in a very noticeable fashion as if the Torah has been split into two Torahs!  Since the family was spending the yom tov together, and the majority of the members of the family had accepted the psak of their local rabbi, even the daughter should follow that opinion on this occasion, and only keep one day. On some other occasion, if the daughter should happen to visit Eretz Yisroel again for a yom tov without the rest of the family, she ought to follow the psak of her rabbi.
The second case came two weeks later, when I was consulted by a rabbi who was going to Eretz Yisroel for yom tov with a group of baalei batim from his shul. They were all going to spend the yom tov together. The majority of his group was clearly going to observe only one day of yom tov, no matter what the rabbi would tell them. They knew that such an opinion is floating about, and were going to follow it this yom tov, as they had already done in the past. The question was whether it makes sense for some of the group to observe two days yom tov, when the majority of the group was not going to. Here again I thought that since the majority of the group planned to follow the one view, that it was not proper for the minority to follow the opposing view. In the event that the minority of the group should visit Eretz Yisroel on another occasion for a yom tov, they should ask again what to do. The reason for this psak was that the minority ought to follow the practice of the majority provided that the majority is following a valid halachik opinion.
Of course, it is self understood that in both cases, if the family (or the group of baalei batim) turns out to be staying in a hotel where the majority of the guests will be observing the second day of yom tov, then that majority ought to be followed.
 Gemara Beitza (4b)
 See Yom Tov Sheni Khilchaso (Fried, 1998) pg. 48, and pg. 215 (quoting Rav Auerbach).
 Rav A.Y. Hakohen Kook used to follow this view (see Sifrei Rav Neirah)
 See Nefesh Horav, pg. 84-85
 For a discussion of the halachik significance of the concept of "eilu v'eilu divrei Elokim Chayim" see Be'ikvei Hatzohn, pg. 259
 See Yevamos (13b - 14a), and Beitza (20a) quoting a Tosefta Chagiga