December 21st of the year 2012 is the day time as we know it will end.

"So at least claim the Maya's, that ancient civilization that lived in the Mesoamerica's since 2,600 BC. The Maya's had an extremely complicated method of keeping track of time, based on three separate calendars. The most important, most encompassing of these calendars holds the `Long Count': the period from the beginning until the end of time. And on December 21st 2012, the Long Count expires. It will be point zero. Time will be up for the Universe. It will be, literally, the end of days..." http://www.exitmundi.nl/Maya.htm
THE END OF THE WORLD by Skeeter Davis: