Wikipedia: Islamic Calendar
Encyclopedia article about the Islamic or Hijri calendar, used to date events in predominantly Muslim countries and to determine the proper day on which to celebrate Muslim holy days.
Islamic Finder: Hijiri Calendar
Hijiri to Gregorian date converter offering Ramadan calendar dates and other Islamic event dates.
Astronomy for Islam
Islamic calendar, date conversion, prayer schedules, and Qibla direction.
Ramadan calendar. Customize to year and location for precise calendar times for Ramadan.
Islamic Calendar, The
Backgrounder of the Islamic calendar with sections on what an Islamic year looks like and the difference in years with the Gregorian calendar.