Christians know that the Christian calendar starts from the birth of Jesus. Muslims know that the Muslim calendar begins with the flight of Mohammed from Mecca to Medina.

But most Jews would be hard pressed to explain what happened 5750 years ago and why the Jewish calendar begins with that event, which will be commemorated this year on Friday evening.

Rosh Hashanah, the Jewish New Year, begins the introspective 10-day period called the High Holy Days, culminating at sundown on Yom Kippur, Oct. 9.

By analogy to the Christian and Muslim calendars, it might be expected that the Jewish calendar would start either from the birth of Abraham (the first Jew) or from the Exodus out of Egypt (the birth of the Jewish people).


Choose Starting Point

Yet the rabbis in the 2nd Century who made up the current Jewish calendar chose as their starting point the estimated time that Adam left the Garden of Eden.

The Hebrew word “Adam” means humankind--the species. The first Adam represents civilized humankind. The exit of Adam from the Garden of Eden symbolizes the transition of humankind from a largely Stone Age state of hunters and gatherers to the more advanced Bronze Age society of farmers and city dwellers.

When did this take place? The most famous attempt to calculate “the beginning” was that of James Ussher, an Irish bishop who wrote a book on biblical chronology in the early 1650s. He sets the date of the departure from the Garden of Eden in the year 4004 BC.


Although it might seem like a simple task to add up the life spans of the generations mentioned in the Bible, it is not. First of all, the Greek translation, the Septuagint, reports very different figures from those given in the Hebrew Bible.

160-Year Underestimate

A second problem arises when there is no continuity of generations. Thus the estimate of the time back to Adam made by Rabbi Yosi ben Halafta in his 2nd-Century book, “Seder Olam Rabbah,” was too short because Rabbi Yosi underestimated the length of the Persian Empire by about 160 years. The current Jewish calendar is based on his chronology. According to this, Adam exited the Garden of Eden and became civilized in the year 3760 BC. With the addition of the 160 years, Rabbi Yosi’s date is within a century of Bishop Ussher’s.

Another way to estimate when humankind became civilized is to use the evidence of archeology. Most archeologists believe this fundamental development in human evolution took place in the Tigris/Euphrates Valley almost 6,000 years ago.