Muslims follow a lunar calendar whose twelve months add up to 354 days. In a cycle of thirty lunar years, eleven are leap years, with one day added to the last month. During Muhammad’s time the lunar months were associated with seasons (Ramadan means “extreme heat,” Rabi’ “rainy season,” and Jumada “dry season,” for example). As in the Jewish calendar, the pre-Islamic year maintained its connection with agricultural cycles and seasons by the intercalation of a whole month in certain years. Since the practice of intercalation ended around Muhammad’s time, the Islamic lunar year rotates backward eleven days each year in relation to the Gregorian solar year. If Ramadan, for example, begins on January 12 this year, next year it will begin on January 1, and so on. Certain practical results of this backward rotation are worth noting because of the way timing can affect religious practice. When Ramadan (the ninth month) occurs in the dead of winter, when days are shortest, the fast from sunrise to sunset is less arduous than when Ramadan falls during the height of summer. Pilgrimage to Mecca can also be more strenuous when the season of Hajj (in the twelfth month) occurs during the hottest season. Muslims the world over therefore must learn to work with two different systems of marking special times. Muslims begin their count of years with the Hijra of 622. Approximately every thirty-three years the beginnings of the Islamic lunar and Gregorian solar years roughly coincide.