The Muslim faith has a different calender. It is the Hijri calendar. It follows the cycle of the moon. There are twelve months, but, they are shortened by a few days than the Gregorian Calender. It is believed someday the years of the Hijri calender and the Gregorian calender will meet and then the Hijri calender will have a higher number. However, and oddly, the Hijri calender is taken from the Hebrew practice of basing it on cycles of the moon. The Hijri calender will never come close in number of years of the Jewish calender. It will never surpass it in numbers.
The Hijri calender began with Mohammed's emigration to Medina. The year then was 622 A.D. according to the Gregorian calender.
Islam/Muslim is a schism. It grew out of Christianity and shares many of it's beliefs including the existance of Jesus Christ and Mary, his virgin mother. They view Jesus as a prophet.
There is no cornerstone to the Islamic faiths. They have the Quran as a guideline. Those whom practice the Muslim faith use the Quran as a guide to the “straight way” [Quran 1:6], for living in accordance with the will of God (Allah).
The beliefs are based in the Five Pillars of Islam:
1. Shahadah: The declaration of faith
2. Salat: Prayer
3. Zakat: Charity or concern for the needy
4. Saum: Fasting during Ramadan or self-purification
5. Hajj: The pilgrimage to Mecca
Mohammad disregarded the Ten Commandments. He took a different route. Of any of the Abrahamic religions, the Muslim faith varies the most from each of the others.
