The first six months on the Jewish calendar in chronological order are Nisan, Iyar, Sivan, Tammuz, Av and Elul. The next months are Tishri, Cheshvan, Kislev, Tevet, Shevat and Adar. In leap years, Adar is calledAdar I and is followed by Adar Beit.
Nisan is the first month and it begins in the spring with Passover. Although Passover begins the first month of the calendar, the Jewish New Year holiday is in the month of Tishri. This is the point when the year number changes. The months on the calendar are not Hebrew in origin but are actually Babylonian. They were adopted during the Hebrew exile from Judah to Babylon in 586 B.C.
Each month has a corresponding theme. Nisan's theme is redemption, and Iyar's is self-improvement. Sivan is about the giving of the Torah, while Tammuz is a time to guard the eyes and reflect upon the sin of the golden calf. Av's theme is comfort, for although the first High Priest and both Temples were destroyed during Av, it is seen as a time to reflect on the end of exile and the eventual fulfillment of God's promise to the Hebrews. Elul is about repentance, while Tishri is about strength. Cheshvan is the month of the great flood. Kislev is about rest and Tevet is about Divine Grace. Shevat's theme is the Tree of Life, and Adar's is good fortune.