Answer:
A candle is lit on each of the eight days of Hanukkah.
Hanukkah always starts on the Hebrew calendar date of 25 Kislev, and lasts for eight days. The Hebrew calendar does not line up with the western calendar because it has a completely different leap year system that can shift holidays each year by to 11-28 days.
Here are the coinciding secular dates for the upcoming years. The candle lightings begin on the evening BEFORE the first date:
2011: December 20-28
2012: December 8-16
2013: November 27-December 5
2014: December 16-24
2015: December 6-14