"This month shall be unto you the beginning of months: it shall be the first month of the year to you" (Exo. 12:1-2). "This day came ye out in the month Abib" (Exo. 13:4).
A month is one new moon to the next new moon. "And it shall come to pass, that from one new moon to another (month), and from one Sabbath to another, shall all flesh come to worship before me, saith the LORD" (Isa. 66:23). "In the first month, that is, the month Nisan, in the twelfth year of king Ahasuerus, they cast Pur, that is, the lot, before Haman from day to day, and from month to month, to the twelfth month, that is, the month Adar" (Est. 3:7).
The Lords year is from the first new moon on or after the spring equinox to the next new moon on or after the spring equinox, which means it has no set starting point like the modern calendar.
Here is a table comparing the Lords calendar and today's modern calendar.