With the approaching ‘3-day Yom Tov’ this Shavuos, and the accompanying sociological challenges, this essay will reexamine the origins of Yom Tov Sheini shel Goluyos.
Most are familiar with the Gemara in Beitzah 4b:
In early times they used to light bonfires, but on account of the mischief of the Samaritans the Rabbis ordained that messengers should go forth. But now that we are well acquainted with the fixing of the new moon, why do we observe two days? — Because they sent from there: take care of the custom of your fathers in your hands; for it might happen that the government might issue an antisemitic decree and it will cause a blunder.
Rashi explains that the inability to learn Torah would lead to confusion regarding the fixing of the calendar. Were they only to observe one day of Yom Tov, their negligence might result in an error concerning the calculation and setting of the correct day of Yom Tov.
The Meshech Chochma (Bo ch.12 s.v. Uvazeh), however, asks: What makes the Diaspora unique in this regard? Theoretically, such a decree could also be enacted in Eretz Yisrael, causing confusion around the correct day of Yom Tov!