A month was calculated by ancient peoples as the time between two full moons, or the number of days required for the moon to circle the earth. This measurement, called the lunar month and it is equal to 29 days 12 hours 44 minutes . The Islamic year consists of 12 lunar months. One hundred and sixty five years after the Quran was revealed to Mohammad and in the year 1582 , to be specific, the Italians, French, Portuguese and the Spanish were first to adopt the modern or Gregorian calendar. In this calendar the measurement of a year is based on one revolution of the earth around the sun. The length of the months is approximately one twelfth of a year (28 to 31 days) and is adjusted to fit the 12 months into what is called a seasonal, tropical, or solar year.
This New Style calendar, was slowly adopted throughout Europe. It is used today throughout most of the Western world and in parts of Asia. When the Gregorian calendar was adopted in Great Britain in 1752, a correction of an 11-day discrepancy was made; the day after Sept. 2, 1752, became September 14. The Soviet Union adopted the Gregorian calendar in 1918, and Greece adopted it in 1923.
The variations among the many calendars in use from ancient to modern times have been caused by the inaccuracy of determinations of the exact duration of the year. The difference between the Gregorian calendar (solar) which was first adopted in the 16th century and the Islamic calendar (lunar) which was adopted in Mohammad's time is 11 days per year. This makes the Quranic verse mentioned above valid in both calendar systems, the one that was followed during Mohammad's times and the one that was adopted 165 years later because:
300 years X 11 days per year = 3300 days A solar year contains 365 days, 5 hr, 48 min, and 45.5 sec. (about 365.24 days) So, 3300 days / 365.24 days per Solar year = 9.03 years In terms of years the above figure is Nine years, which was added to the three hundred years 165 years after it was mentioned in the Holy Quran.
