THE BIBLICAL CALENDAR IS LUNAR

Rosh Chodesh was the first commandment given to the nation of Israel when they were redeemed from Egypt (Mitzrayim). In Exodus (Shemot) 12:1-2 it is written:

Exodus 12:1 And the Lord spake unto Moses and Aaron in the land of Egypt, saying,

Exodus 12:2 This month shall be unto you the beginning of months: it shall be the first month of the year to you.

Exodus 13:4 This day came ye out in the month Abib.