ROSH CHODESH NEW MOON
And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years Bereshit 1:14
He made the moon to mark the seasons; the sun knows its time for setting. Tehillim 104:19
“The people of the land shall also worship at the doorway of that gate before YHWH on the sabbaths and on the new moons.” Ezekiel 46:3
A new moon day is not known exactly when it will happen so it is celebrated for 2 days. A new moon day occurs when the crescent appears to mark the beginning of a new month. Hanoch (Enoch) 78:12