Notes: All timings are represented in 24+ hour notation in local time of Fairfield, United States with DST adjustment (if applicable).
Hours past midnight are higher than 24:00 and fall on next day. In Panchang day starts and ends with sunrise.
The most of the India observe Deepavali when Amavasya Tithi prevails during Pradosh i.e. just after sunset. However, in Tamil Nadu Deepavali is observed when Chaturdashi Tithi prevails during Brahma Muhurat i.e. just before sunrise.
In Tamil Nadu, people get up early on Deepavali day, take bath before sunrise, wear new clothes, perform Puja, lit earthen lamps and play crackers. Apart from Tamil Nadu, in neighboring state Karnataka also, people follow the same rituals as that of Tamil Nadu on Chaturdashi Tithi. Hence, in Tamil Nadu and Karnataka, Chaturdashi Tithi is the main day during Deepavali and unlike rest of India earthen lamps and crackers are lit during dawn and not after dusk.
It is interesting to note that unlike North India, which celebrates Deepavali as the arrival of Lord Rama to Ayodhya, in Tamil Nadu and Karnataka Deepavali is celebrated as killing of demon Narakasura by Goddess Satyabhama and Lord Krishna. It is also important to note that, depending on the start and end timings of Chaturdashi and Amavasya Tithi in lunar calendar, most significant day during Diwali festivities in Tamil Nadu and Karnataka might fall one day before or on the same day of Deepavali in rest of India.
The rituals which are observed in Tamil Nadu and Karnataka on Chaturdashi are also observed in other parts of India but with the name of Naraka Chaturdashi and Abhyang Snan. However, in other states it is oil bath which is more significant on the day of Naraka Chaturdashi.