Two Days Rosh Hashanah, Eruvin And Eggs

Following the destruction of the Second Temple, the dilemma of the Levites was no longer a concern. Accordingly, it was decreed that the testimony of witnesses arriving after Minchah on the 30th of Elul would once again be accepted, thereby rendering Rosh Hashanah one day. If witnesses did not arrive by nightfall of the 30th, Rosh Hashanah would be two days. The decree did not, however, apply to the Diaspora, where it could not be known on the 30th day whether the witnesses had arrived or not. Accordingly, Rosh Hashanah in the Diaspora remained two days by decree. The Babylonian rabbis who came to Israel applied the same decree there. Although we now know which day is genuinely Rosh Hashanah, we continue to celebrate two days everywhere out of respect for the tradition of our ancestors (minhag avoteichem beyedeichem).