Jewish Communities Since Then
The commentaries debate the following interesting question: What should new Jewish communities – settled after the time of the rabbinic enactment – do? They do not have a “custom of their forefathers” to guard – neither to observe one day, nor two.
Where Messengers Reached
The Rambam (Hilchos Kiddush HaChodesh, ch. 5) writes that places where beis din’s messengers were once able to reach should keep one day of Yom Tov today – even in chutz la’aretz. Conversely, wherever the messengers could not reach should keep two days of Yom Tov – even in Eretz Yisrael. The general principle that one day is observed in Eretz Yisrael and two in chutz la’aretz applies only to those places where we are uncertain if the messengers could have reached. Those places should conduct themselves according to the custom of the majority of surrounding cities. (And in Eretz Yisrael the majority keeps one day, and in chutz la’aretz the majority keeps two.)
The Chazon Ish (O.C. 132:3) explains that this is not only a b’dieved compromise based on uncertainty. Rather, when Hillel and his beis din originally enacted the rabbinic decree to keep two days of Yom Tov, they decreed that those communities whose custom is known should continue to follow their custom, and those communities whose custom is not known should keep one day in Eretz Yisrael, and two days in chutz la’aretz. New communities have the status of communities with no known custom.
Eretz Yisrael And Chutz La’aretz
However, the Ritva (Rosh Hashana 18a; Sukka 43a) disagrees with the Rambam and rules that Hillel and his beis din made a stark distinction between Eretz Yisrael and chutz la’aretz. All places in Eretz Yisrael must keep one day of Yom Tov, and all communities in chutz la’aretz must keep two – regardless of whether beis din’s messengers could have reached them. New communities are no different than old communities. The Acharonim note that the Ritva’s opinion is supported by the Gaonim and many Rishonim, and is accepted as normative in halacha (see Yom Tov Sheini K’Hilchoso, Appendix 4).