Kali Chaudas is also known as Bhut Chaturdashi. Kali Chaudas is mainly observed in Western states especially in Gujarat.
Kali Chaudas is observed during Chaturdashi Tithi during Diwali festivity. However Kali Chaudas day should not be mixed with Roop Chaudas and Narak Chaturdashi as it might fall one day before of Narak Chaturdashi. The day of Kali Chaudas is decided when Chaturdashi prevails during midnight which as per Panchang is known as Maha Nishita time.