In the name of Allah, Most Gracious, Most Merciful
In the Holy Quran we read:
"They ask thee about the new moons. Say, These are means for measuring time for people's affairs and for the Pilgrimage" (Holy Quran, Ch. 2 V. 190)
Islam has made use of both the lunar and solar system of measuring times. Where worship is to be performed in different parts of the day the solar system of reckoning time is used as in the five daily Prayers or for the beginning and breaking of the fast, and where worship is to be completed within a particular month or part thereof, the lunar system is used, as in the determination of the month or part thereof, the lunar system is used, as in the determination of the month of fasting or fixing the time of Hajj or other festivals.
To calculate conversions from one calendar year to the other the following formula is used:
G = H - ( (3 * H) / 100 ) + 622
H = G + ( ( G - 622) / 32 ) - 622
Where G = Gregorian year (AD)
H = Hijra year (AH)
Thus 2000 AD is 1421 AH
Islamic calendar consists of twelve lunar months. Each month may be of 29 or 30 days depending on the sighting of the new moon.
An lunar year has, on average, 355 days. This is 10 days less than the solar year. Hence an Islamic year is moved ahead 10 days each year in solar calendar year.
Following are the names of the Islamic months:
1. Muharram ul Haram
11. Dhul Qadah
12. Dhul Hijja
The Holy Quran states:
"The number of months with Allah has been twelve months by Allah's ordinance since the day He created the heavens and the earth. Of these four are known as sacred" (Holy Quran, ch., v 36)Muharram, Rajab, Dhul Qadah and Dhul Hijja are considered to be sacred months. Fighting during these sacred months is considered to be a sin.