The NYSE is operated by NYSE Euronext (NYSE: NYX), which was formed by the NYSE's 2007 merger with the fully electronic stock exchange Euronext.
So I went to the Euronext websitehttp://www.nyx.com
and clicked on holidays and hours then morehttp://www.nyx.com/holidays-and-hours/nyse
I don't see an early close for December 31.
*Each market will close early at 1:00 p.m. on Friday, November 23, 2012, Friday, November 29, 2013 and Friday, November 28, 2014 (the day after Thanksgiving).
**Each market will close early at 1:00 p.m. on Tuesday, July 3, 2012, Wednesday, July 3, 2013 and Thursday, July 3, 2014.
***Each market will close early at 1:00 p.m. on Monday, December 24, 2012, Tuesday, December 24, 2013 and Wednesday, December 24, 2014.