Islamic Voice
Rajab 1422
October 2001
Volume 15-10 No:178

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Scientific and Mathematical Lunar Calendars

Scientific and Mathematical Lunar Calendars

Non Seasonal (Islamic) and Seasonal Lunar calendar could be perfected and important dates could be predetermined with precision as by now lunar movement are well documented.

Dr. Syed Abdul Zahir

In the medieval period only the lunar calendar was existing. Much later the calendar became lunisolar. The Romans and Christians started with a purely solar calendar from 45 B.C., while the other major communities, the Hindus, the Jews and the Chinese continued with the seasonal lunisolar calendar. And much later, because of the irregularity in the introduction of an intercalary month (Quran IX- 36,37) the Muslims in Arabia adopted a purely lunar non-seasonal calendar from July 16, 622 AD, that is the Hejira calendar during the life time of our Prophet (Pbuh). Around this time all the three calendars i.e., the lunar, the lunisolar and the solar calendars were existing and were followed in different communities. The Christians have been following the solar calendar, either Julian or Gregorian, but all their festival dates-Good Friday, Easter, Ash Wednesday etc. are calculated as per the lunisolar calendar except the Christmas day.

Mathematical Non-Seasonal Lunar Calendar (Islamic): This calendar is being followed only by the Muslims all over the world. Its only disadvantage is that it is non-seasonal and keeps going back by 10 to 12 days each year relative to the widely used Christian solar year, that is why all the other major communities, the Hindus, the Jews and the Chinese have adopted the seasonal lunisolar calendar and a fresh lunar month is born with the birth of the new moon, whose accurate timings are available not only for the future years but also for the past. I am proud to state that I am in possession of the new moon timings of the lifetime period of our beloved Prophet (Pbuh) i.e., from 569 to 630 AD.

This calendar is advantageous to the Muslims especially during the fasting month of Ramadan. If the calendar followed in Islam were to be solar, the community living in one hemisphere would have had the lifetime disadvantage of fasting for a month continuously in hot summer and longer days while those living in the other hemisphere would have had the life long advantage of fasting in the cooler and shorter days. Since Muslims follow a pure lunar calendar the month of Ramadan keeps rotating about every 32 to 33 years, hence the advantages and the disadvantages are equally shared by the Muslims all over the globe. At present it is advantageous for the people in the Northern Hemisphere, while the Muslims living in the Southern Hemisphere are having to fast in hot summer and longer days. After about a period of 15 years from now the conditions are going to be reversed, that will run to about 15 years.

For example, I had performed my first Haj in the year 1971 on February 5, (9th day of Zul Hijja) and next the Haj will fall around the same date in the year 2003 AD, after a period of about 32 years. This non-seasonal lunar calendar is purely scientific and mathematical and as such there is no room for any one toward problem or doubts.

Please note carefully how it is worked out:

One lunar month or one orbit of the moon around the earth or from one conjunction (new moon) to the next one the period is 29 days, 12 hrs, 44 minutes and 3 seconds equal to 29.5306 days. Hence in one year or 12 months there are 12x29.5306 = 354.3672 days. Therefore each year there are 354 days and a fraction of 0.3672 days. The fraction is equal to about 8 hours or roughly 1/3 of a day.

Hence in a period of every 3 years, two years may have 354 days and the third year, a leap year will have 355 days. This adjustment looks fair. But more appropriate would be that a block period or a cycle of 30 years having 11 leap years and 19 common years: one cycle 19x 354= 6726 days (10631 days) 11x 355= 3905 days (10631 days)

It may be noted that the two multiples are almost exact and the fraction of 0.016 day in a period of 30 years is insignificant.

The 11 leap years generally accepted in the Islamic world are: 2, 5, 7, 10, 13, 16, 18, 21, 24, 26 and 29th years. In each year, the 12 months have 30 and 29 days alternating with the first month of Muharram having 30 days and the 12th month of Zul Hijja having 29 days. In each of the 11 leap years the extra day is added to the 12th month, Zulhijja, which has 30 days instead of 29 days. The Eidain (the two festivals of Eid) are celebrated according to the moon sighting but the fixed scientific calendar does not change. Almost all the Arab countries follow this type of calendar and get the calendar printed in advance as is done for the English calendar in our countries.

This year 1422 AH is the 12th year of the current block or cycle. This calendar can be prepared for the next few centuries without much difficulty.


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