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What happens if people follow a lunar calendar without trying to correct it to match Earth’s orbit around the Sun? The Islamic calendar used by Muslims provides a real-world answer. Muslims are aware of the difference between the solar and lunar calendars, but they have chosen to use the lunar calendar to set the dates for their holy days. As a result, each year the month of Ramadan, which is the ninth month in the Islamic calendar, occurs about 11 days earlier than the previous year. During Ramadan, faithful Muslims do not eat or drink between sunrise and sunset. (Certain groups of people are not required to fast, however, such as the sick, pregnant women, or young children.) If Ramadan falls during the winter, it is not as difficult to fast and go without water because the days are short and cool. Fifteen years later, however, Ramadan will fall during the middle of summer, when the days are long and hot. In North America, only a few Indian tribes tried to correlate the Moons and years more precisely. The Creek Indians supposedly added a Moon cycle between each pair of years. A tribe of the Dakota, Lakota, and Nakota (formerly known as Sioux) and the Chippewa added a “lost Moon” lunar cycle after 30 Moons had gone by, presumably to solve the difference between the solar and lunar years. ■ Calendars in Use Around the World Today There are still several different calendars in use around the world. Some are based on the Sun, some on the Moon, some on both (solilunar calendars), and some on factors that are not related to either. The five major solar world calendars in use today are the Gregorian, Islamic, Chinese, Jewish, and Hindu calendars. Because the Gregorian and Chinese New

Year are the two largest New Year’s celebrations in the world, their calendars are examined in greater detail below. What is common among all five of these calendars is that there are seven days in a week and 12 months in a year, but they differ as to when a new day begins. Get a brief history of the modern calendar.

According to the Gregorian (or Western) calendar, a day begins at midnight. In the Islamic calendar, the day begins at sunset. The Chinese define the start of a day at exactly 11:00 p.m. The Jewish calendar day begins at sundown or dusk. For those following the Hindu calendar, the day begins at sunrise or dawn.

Origins of a Calendar Year n

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