Determining the appearance of the new moon through eyewitness testimony was always accompanied with anticipation and uncertainty. The new moon or new year offerings could not be commenced until two witnesses had arrived and testified before the Great Sanhedrin, to the satisfaction of the Great Sanhedrin. It was customary for people to begin observing the holiday as a precautionary measure, even before the testimony had been offered or accepted. It is told that on one occasion, witnesses arrived at dusk. In the rush and ensuing confusion, the Levites neglected to sing their daily psalm. In order to prevent a recurrence, the sages ruled that testimony would henceforth be accepted only up to the time of the daily afternoon offering. If witnesses failed to arrive by this time, the following day would nevertheless be observed as Rosh HaShana.