2. Holy book and holy days

 The holy book of Islam is Qur'an and is also called Koran.
Quran is the final scripture that Muslims believe in, because all of the previous holy scriptures had been corrupted or lost. The major, previous holy scriptures are Torah, Psalms, and Gospel. Quran is composed of verses (Ayah) that make up 114 chapters (suras) of unequal length which are classified either as Meccan or Medinan depending upon their place and time of revelation. Muslims believe the Quran to be verbally revealed through angel Jibrīl (Gabriel) from God to Muhammad gradually over a period of approximately 23 years beginning in 610 CE, when Muhammad was 40, and concluding in 632 CE, the year of his death.


The six most important Islamic holy days are New Years, Ashura, Mawlid, Ramadan, Id al-Fitr, and Id al-Adha.
New Year is celebrated on the beginning of the first lunar month and also called Al-Hijra or Muharram.
For Sunni Muslims, Ashura is a day of fasting that was originally observed by Jews to recall when God saved the Children of Israel from the Pharoah in Egypt. Muhammad made it compulsory for Muslims as well.
Mawlid is a celebration of the birthday of the Prophet Muhammad, the founder of Islam in 570 CE. Sunni Muslims observed it on the 12th of the lunar month of Rabi'-ul-Awwal in the Islamic calendar.
Ramadan is the holiest period in the Islamic year which is held during the entire 9th lunar month of the year. This was the month in which the Qura'n was revealed to the Prophet Muhammad. Muslims are expected to fast from sunup to sundown.
Id al-Fitr is the first day of the 10th month which is the period of rejoicing.
Id al-Adha, also known as the Feast of Sacrifice or Day of Sacrifice, occurs during the 12th month of the lunar month, following the Hajj imediately.

http://www.history.com/videos/history-of-ramadan#history-of-ramadan (Ramadan Video Clip)