Rarely Rosh Hashanah, Ramadan coincide: Once every 33 years
Everybody knows that there are 365 days in the solar year. But how many know the number of days in a lunar year? The answer is 354, 11 days fewer than in the solar calendar. Judaism and Islam, which both observe a lunar calendar, treat this disparity differently.
This year the Muslim holy month of Ramadan, a period of daylight fasting and prayer, began on October 4—the same day as Rosh Hashanah, the start of the introspective High Holy Days that conclude with Yom Kippur.
Many Jewish holidays, including the fall harvest festival of Sukkot and the spring observance of Passover, are connected to agricultural and seasonal cycles. It would be unacceptable for these holidays to “migrate” throughout the year, with Passover, for example, celebrated during the coldest time of winter.
To correct for this problem, every three years (when the 11-day annual discrepancy between the solar and lunar calendars totals around 30 days) the Jewish calendar inserts a 13th month into its cycle.
The Muslim calendar, however, follows a strictly lunar schedule of a 354-day year because Islam’s major holidays are not connected to specific seasons or agricultural harvests. Accordingly, Ramadan and Rosh Hashanah begin on the same day only once every 33 years. –Religion News Service