8 - THE CONVERSION OF A
SOLAR YEAR INTO A LUNAR YEAR

As it has been stated in the chapter captioned PRAYER TIMES in the fourth fascicle, one of the units of measurement of time is the year. Two kinds of years of different lengths are: solar year and lunar year. A solar year is the duration of time in which the earth makes one tour around the sun: which is 365.242 solar days. Lunar year is the length of time it takes for the moon to make 12 rotations around the earth: this takes an average of 354.367 solar days. Therefore, a solar year is 10.875 days longer than a lunar year. Regarding the starting point of time, two types of calendars are being used: Hegira and Gregorian. The Gregorian one is supposed to have started at the birthday of the Prophet Îsâ ‘alaihis-salâm’, However, contrary to the common belief, it is written in, Cosmographia, by Hasîb Bey, that King Charles IX of France ordered in 970 [1563 A.D.] that the new year should start on 1 January. The Hegira calendar starts with the year when our Prophet (sallallâhu alaihi wa sallam) migrated to the city of Medina. The starting day of the Hegira solar year is the 20th of the Gregorian September, which was Monday, the 7th of September of the Roman year, when he entered Medina. This information is written in further detail in the calendar of Abuz-ziya, dated 1310 [1893 A.D.]. The Persian solar year starts six months before the Hegira solar year, on the 20th of March, which coincides with the Zoroastrian feast. On the other hand, the starting day of the

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Hegira lunar year is the 16th of July (A.D), the first Friday of the month of Muharram of the same year. The migration of our Prophet (sallalâhu alaihi wa sallam) took place in 622 (A.D.). The beginning of the Hegira lunar year is 196 days (0.54 years) after the completion of the year 621 A.D. The Hegira solar year began 262 days (0.72 years) after the completion of the year 621 A.D. So, the beginning of the Hegira solar year is 66 days (0.18 years) later than the Hegira lunar year. If 0.18 years is added to the number of the Hegira solar year, the number of the Hegira solar year also will start on the 16th of July. Due to the 10.875 days’ difference in a year, for every 32.59 years of the Hegira solar calendar, 33.59 years have elapsed of the Hegira lunar calendar. If the number of lunar years is multiplied by the quotient of 32.59 ÷ 33.5 = 0.97023 the product will be the number of solar years. If the number of Hegira solar years is multiplied by the quotient of 33.59 ÷ 32.59 = 1.0307 the product will be the number of lunar years.

Let us find out the Hegira solar year which coincides with the beginning of the lunar year 1404. Since a year begins after the last day of the previous year, and if the solar year had also started on the 16th of July, then the number of solar years would simply be 1403 x 0.97023 = 1361.23. But, since a solar year starts 0.18 years later than the 16th of July, 0.18 years is subtracted and then 1361 is taken: 1361.05 - 1361 = 0.05. Therefore, the beginning of the Hegira solar year becomes 0.05 x 12 = 0.6; first month’s 0.6 x 30 = 18th day of the year 1362.

Let us find out the lunar year which coincides with the beginning of the 1362 Hegira solar year: If the lunar calendar had started on the 20th of September, too, it would be 1361 x 1.0307 = 1402.78, and an 0.18 year excess of that number would be 1402.96 and taking 1402 from it 1402.96 -140 2 = 0.96 and 0.96 x 12 = 11.52; half of the twelfth month of the year 1403.

Let us find out the starting dates of the Hegira years which coincides with the beginning of 1984 A.D. The Hegira solar year which coincides with the beginning of 1984 A.D. is 1984 - 622 = 1362. The difference between the 20th of September and the 1st of January is 103 days (0.28 years). We have already found that the lunar year which coincides with the beginning of the solar year 1362 is 1402.96. So, the lunar year would become 1402.96 + 0.2 8= 1403.24. That means 0.24 x 12 = 2.88 or the third month (0.88 x 30 = 26.4) or the twenty-seventh day of the lunar year 1404.

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