The Jewish people who returned to their homeland after their period of exile in Babylonia and Persia restored their worship rituals. These included the celebration of each new moon, which marked the beginning of a new month in their calendar. Offerings and sacrifices were made to atone for their sins committed during the previous month. The new moon celebration is also referred to in Numbers 10:10

EZRA 3:5 – Afterward [the Israelites] offered the continual burnt offering, both of the new moons, and of all the set feast of the LORD