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, like the middle days of Passover and Sukkot.
When a Hebrew calendar month is 30 days long, day 30 is considered Rosh Chodesh of the next month. Then Rosh Chodesh is two days long: day 30 of the old month and day 1 of the new month.
- Kosofsky, Scott-Martin. The Book of Customs: A Complete Handbook for the Jewish Year. San Francisco: Harper San Francisco, 2004. p.91