Dec. 21 has arrived for some parts of the world, but some people would rather not be too complacent. Others believe the exact hour of the Mayan calendar end of the world prediction reconciles with the time of the December solstice, which is at 11:12 UTC.

Mayan Calendar Time Zone: Dec. 21, 2012 at 11:12 (UTC)?

The December solstice marks the arrival of winter in the northern hemisphere (North and Central America, Europe, Asia, Northern Africa), and summer in the southern hemisphere (Australia, New Zealand, South America, Southern Africa). This year's solstice occurs at 11:12 am UTC, according to timeanddate.com.

The solstice happens twice a year. It pertains to the position of the sun (highest or lowest) with respect to the celestial equator. It signals the changing of the seasons. This change in seasons is presumed by many to have guided the Mayans in predicting the end of the world.

Mayan Calendar 2012 Apocalypse Prediction: 'You still have to do your holiday shopping' - Professor

Some scientists have argued that the Mayans did not predict the end of the world; they merely marked the end of a calendar cycle. This translates to the beginning of another cycle and not the apocalypse. Still, doomsday fears continued to get attention.

NASA: Why the world didn't end on Dec. 21

(Read: Mayan Calendar 2012 End of the World? NASA Films 'Why the world didn't end on 12/21/2012' [VIDEO])

NASA has prepared a documentary to explain why the world would still exist by Dec. 22. It made a video meant to be released on Dec. 22, but it was released ahead of time to answer hundreds of questions from the public daily.

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