Naraka Chaturdashi is a Hindu festival, which falls on the second day of the festival of Diwali.
Kali means Dark (evil) and Chaudas - Fourteenth. Thus, celebrated on the 14th day of the dark half of Āshwin month, Kali Chaudas is the day allotted to the worship of Maha-Kali or Shakti and is believed that on this day Kali killed the wickedest NARAKASURA. Also referred to as Narak-Chaturdashi, Kali Chaudas is day to abolish laziness and evil which create hell in our life and shine light on life. The strength to protect others is referred as Kali, and if its used for God's work is called Mahakali.
(... from Wikipedia on 2012-04-18 00:12:07)