The current date on the Hebrew (Jewish) calendar represents the number of years since Creation. This number was determined by adding all the ages of people mentioned in the Bible back to the first day. This does not mean that Jews believe that the universe is only some 5,700 years old though. Indeed many Jews, from Reform to Orthodox, accept the idea that the first six "days" of creation may not have been the 24-hour days we recognize today. For instance, when God separated the waters that process could have taken thousands of years.