And G-d spoke to Moses and Aaron in the land of Egypt, saying: This
chodesh (new moon, month) shall be for you the head of months; it shall be for you the first of the months of the year (Exodus 12:2)
There are two "heads" to the Jewish year. The 1st of Tishrei (Rosh Hashanah), the day of the creation of man, is the head of the natural year -- the year which the Jew shares with all of creation. The month of Nissan, marking the Exodus and the birth of Israel, is the head of a miraculous year: a dimension of time, inhabited solely by the Jew, in which the miraculous -- i.e., the power to transcend nature and norm -- is the very stuff and substance of life.
(The Chassidic Masters)