The Bible shows that each New Full Moon is the beginning of a new month.
14. And God said, “Let there be lights in the firmament of the heavens to divide between the day and the night, and let them be for signs, and for appointed or set times which are the Feasts and Holy Days of God’s seasons, and for days and years;
15. And let them be for lights in the firmament of the heavens to give light upon the earth.” And it was so.
16. And God had made two great lights, the greater light to rule the day and the lesser light to rule the night; and God had made the stars also.
17. And God set them in the firmament of the heavens to give light upon the earth,
18. And to rule over the day and over the night, and to divide between the light and the darkness. And God saw that it was good.