The Extra Day
Answer:Jewish festivals are celebrated for one day in Israel and two days in the Diaspora. This goes back to the time when the beginning of each Jewish month was determined by the appearance of the new moon and its consecration by the Sanhedrin in Jerusalem. Since it took time to communicate the beginning of the month to the Diaspora, these communities frequently did not know exactly when the festival would start. As the start of the new month could vary by a maximum of one day, Diaspora communities observed the festivals over two days, to make sure that they had it right.
The Jewish calendar was already fixed by the time of the Talmud, and this made adding a second day to the festivals unnecessary. The Talmud asks: [BT Beitza 4b]But now that we are well acquainted with the fixing of the new moon, why do we observe two days? – Because they sent [word] from there [Palestine]: Give heed to the customs of your ancestors; for it might happen that the government might issue a decree and it and the custom will be lost.Thus, we have continued to observe one day for a festival in Israel and two in the Diaspora.
When there is a difference of custom between two communities, and someone travels from one community to the other, the rule is [Mishna Pesachim 4:1]:we lay upon him the restrictions of the place whence he departed and the restrictions of the place whither he has gone.Following this, we would expect both a person who goes from the Diaspora to Israel, or vice versa, to observe the more strict custom. Thus, in any case where a person travels, we would expect the norm to be two days observance.
R. Tzvi Ashkenzi [Germany, Holland; 17th Century] known as the Chacham Tzvi, has a novel approach to the problem. He considered the question of two day festivals as different from other customs, where in principle one may choose whether to observe the custom or not. Celebrating two days for a festival is not just a strict observance if there is no reason to do so; it is actually forbidden because it involves saying the wrong prayers and transgressing the biblical prohibition of not adding new commandments to the Torah. He therefore claims that the second day of the festival is not a local custom and that the rules governing local customs do not apply to it.
In other words, at the time the custom was established, anyone who was in the Diaspora [whether they were residents or tourists] was unsure of the date, and therefore had to observe two days. Anyone in Israel knew the correct date and only observed one day. That was the custom of all Jews. Therefore today, anyone who comes to Israel should only observe one day of the festival, but Israelis travelling abroad should observe two, together with the local Jewish community.
Most Rabbis follow the traditional interpretation that each person carries their local customs with them when they travel. The Chacham Tzvi has a unique position, which is both coherent and compelling.
Rabbi Chaim Weiner
Based on Responsa of the Chacham Tzvi 167
Rabbi Chaim Weiner – Based on Responsa of the Chacham Tzvi 167