The Islamic holy month of Ramadan is set to begin. Here's what you need to know about the period and how it's observed.

making the Islamic year 10 to 12 days shorter than the solar year. As a result, the months of the Hijri calendar gradually shift through the seasons, completing a full cycle every three decades or so.

Ramadan is the ninth month of the Islamic, or Hijri, calendar ... year as the Muslim faith follows a lunar calendar that is 11 days shorter than the solar calendar. Adherents to the Islamic ...