Rosh Chodesh

Rosh Chodesh or Rosh Hodesh (Hebrew: ראש חודש‎; trans. Beginning of the Month; lit. Head of the Month) is the name for the first day of every month in the Hebrew calendar, marked by the birth of a new moon. It is considered a minor holiday, akin to the intermediate days of Passover and Sukkot.

Origin

The Book of Exodus establishes the beginning of the Hebrew calendar:

In the Book of Numbers, God speaks of the celebration of the new moon to Moses:

In Psalm 81:3 both new and full moon are mentioned as a time of recognition by the Hebrews.

The occurrence of Rosh Chodesh was originally confirmed on the testimony of witnesses observing the new moon. After the Sanhedrin declared Rosh Chodesh for either a full month or a defective, 29-day month, news of it would then be communicated throughout Israel and the diaspora.

A custom was developed in which an additional day could be added to the month to ensure that certain holidays (such as Yom Kippur) did not fall on the days before or after Shabbat.