Naraka Chaturdashi is an important day during Deepavali festivities. In most years it is observed one day before of Lakshmi Puja. Naraka Chaturdashi is the second most important day during Deepavali after Lakshmi Puja day. Hence, the day of Naraka Chaturdashi is also known as Choti Deepavali especially in North Indian states.
In most South Indian states including Tamil Nadu, Choti Deepavali is celebrated as Deepavali and it is the most important day during Deepavali.
Naraka Chaturdashi is celebrated as the day when Lord Krishna slayed demon Narakasura. As per the legends of Naraka Chaturdashi, Lord Krishna himself took oil bath after killing demon Narakasura during Brahma Muhurat. Hence the day is considered significant to take ritualistic oil bath before the sunrise.
The day of Naraka Chaturdashi is decided based on lunar calendar. The day when Chaturdashi Tithi prevails during Brahma Muhurat is considered to observe Naraka Chaturdashi. The period of approximately one hour and sixty minutes just before the sunrise is known as Brahma Muhurat.
As per Purnimanta Hindu calendar -
Krishna Paksha Chaturdashi (14th day) of Kartik (8th month)
As per Amanta Hindu calendar -
Krishna Paksha Chaturdashi (14th day) of Ashwin (7th month)