YU TORAH and NAALEH.COM Rosh Hashana: Double Days By Shira Smiles

Of all the holidays in the Jewish calendar, only Rosh Hashanah is mandated as a two day holiday both within and outside Eretz Yisroel. Why is this so? Rabbi Dessler in Sanctuaries in Time gives us the simplest, most practical answer. As the Torah commanded, the new moon was to be proclaimed based on the accounts of two eye witnesses coming to the Sanhedrin. The onset for every holiday was then easily calculated from the time the new moon was proclaimed to the day in the month that Hashem designated as the holiday. If the witnesses were delayed, there was little effect on the onset of the holiday, for they were all further into the month. Hashem, however, commanded that Rosh Hashanah be the first day of the month. If the witnesses were delayed, the proper day of observance would be missed. The Sages, therefore, declared Rosh Hashanah to be observed based on their astronomical calculations as the thirtieth day of Elul and set the second day as the first of Tishrei. This would cover either day of an eye witness account should there be a delay in the arrival of the witnesses. This practice of observing two days of Rosh Hashanah (although they have become the first and second days of Tishrei) has since become standardized. click here Summary by Channie Koplowitz Stein.