Jewish Calendar: Solar and Lunar
The Sun, the Moon and the Jews
This becomes somewhat more complicated in the case of the Jewish calendar, for it is still coordinated with the phases of the moon. Indeed, it is that which determines the times of the Jewish holidays. This is of particular importance with those that fall on the new moon and those that are celebrated at the time of the full moon. In addition, since the 12-month lunar year is a few days shorter than a solar year, strict adherence to a lunar calendar would mean that the holidays would eventually take place at the wrong season.
This would mean that every now and then we would celebrate Hanukkah, the mid-winter festival of lights, in the middle of summer and Sukkot, the autumn harvest festival, in the early spring. Therefore, in an attempt to coordinate the traditional lunar year with the solar year Judaism has worked out a system of 19-year cycles, in which there are seven leap years. In distinction to the day added to the secular leap year, the Jewish calendar adds a full month to the end of its year. In this manner the Jewish holidays fluctuate by about a month or so in relationship to the Gregorian calendar, but always fall at the same time of year. It is interesting to note that Islam also follows a lunar calendar. In distinction to Judaism, however, the Islamic calendar is strictly a lunar one and is not coordinated with the solar year. Thus, over the course of time, holidays such as Ramadan, occur at different seasons.
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