Question:
Everyone asks why we, who are in Chutz L'Aretz are still observing two days of Yom Tov. However, why exactly do the inhabitants of Eretz Yisroel only observe one day of Yom Tov? Why doesn't the inyan of Sfeika D'Yoma apply to them? If we do not Mekadesh the Chodesh through testimonies of witnesses, what differences are there?
Answer:
Hello,
The reason they keep two days in chutz la’aretz nowadays (see Beitza 4b), even though we now know according to the calendar when to establish Rosh Chodesh, is that chazal were wary that mistakes might be made. Therefore, they instituted that in chutz la’aretz they should keep the minhag as it was during the time when they were mekadesh the chodesh via witnesses of the new moon. Eretz Yisroel never had the minhag of keeping two days of Yom Tov (except for Rosh Hashana), so they keep only one day.
Best wishes
