Jewish Holidays Jewish holidays are filled with tradition and go back hundreds of years. Some are about solemn occasions but some are more lively and festive. Jews have their own calendar, The Hebrew Calendar. Their calendar is based upon lunar orbits which one cycle is 29.5 days. A lunar year is 354 days which is 11 days less than the solar year which is 365.25 days. The Jewish society add an extra month to the Hebrew calendar seven times out of every 19 years. If they did not do this their holidays would not be celebrated on time. All Jewish holidays begin the evening before the day it is celebrated. There are many holidays that the Jews celebrate that is dependent on their lunar calendar, but the two that depend on it most are Rosh Hashanah
