End of World in 2012? Maya "Doomsday" Calendar Explained (news.nationalgeographic.com)
"It's remotely possible the world will end in December 2012. But don't credit the ancient Maya calendar for predicting it, say experts on the Mesoamerican culture."
"Calendar, any system for dividing time over extended periods, such as days, months, or years, and arranging such divisions in a definite order. "
A Variety of Calendars (webexhibits.org)
"Today almost everyone takes the precision of our calendars for granted, unaware of the long threads spooling out from our clocks and watches backward in time, running through virtually every major revolution in human science, all linked to the measurement of time. "
The Islamic Calendar (webexhibits.org)
"The Islamic calendar (or Hijri calendar) is a purely lunar calendar."