The calendar of the Jewish year is based on two events, both of world significance though one of the two has, in addition, great importance especially for the Jewish nation. The first of these is the Creation of the World, a happening which is considered to have ended almost 5770 years ago; the second, of especially great national importance, is the Exodus from slavery in Egypt, a process which took place nearly three thousand three hundred years ago, culminating in Divine Revelation on Mt. Sinai, the receiving of the Divine word, known as the Torah and the consolidation of the Israelite tribes into a single people.
The calendar of the Jewish year is constructed according to two principles, the one being the relative movements of the sun and the earth and the other – the relative movements of the moon and the earth. The Jewish calendar is thus neither a solar calendar nor a lunar one, though it is characterized strongly by elements of both types.
The calendar of the Jewish year depicts either twelve or thirteen months – the thirteen-month year, somewhat less common than the twelve-month year, being known as a leap year. The first month of the Jewish year is the month of Spring (also known as Nissan), though the year itself begins in the fall – on the first day of the seventh month called Tishre, though its earlier name was the month of the Eternals (in Hebrew: hodesh ha-Eitanim).
The following is a list of the common names of the months of the Jewish calendar:
1. Nissan
2. Iyar
3. Sivan
4. Tammuz
5. Av (Menahem)
6. Elul
7. Tishre
8. Marheshvan
9. Kisle
10. Tevet
11. Shevat
12. Adar (Rishon)
13. Adar (Sheni)