There are number of hindu mythology for the worship of Snake on Nag panchami day like marking the victory of Krishna over Kaliya, farmer and nag, a day for worshiping vasuki naag referred as the king of the Nagas who played vital role during Samudra manthan, it is also believed that Shesha also known as Ananta as the king of the Nagas and worship on this day. According to hindu mythology, on Nag panchami people worship three main deities-Shesha, Takshaka, and Vasuki, the children of the rishi Kashyapa and Kadru, who are the parents of all nagas. Takshaka represents the dangerous aspect of snakes.
As per the Indian Hindu Calendar, Tithi (also spelled Thithi) is the lunar date. There are 30 tithis in each lunar month. These Tithi plays an important role along with nakshatra in Hindu's daily as well as special activities. Nag panchami festival falls on 5th day of the bright half of Shravan month (July/August). Nag Panchami in India is mainly a women festival, observed by married women for the well-being of their husband and children. Pujas and prayers are held in Naga temples across the state.
Nag panchami 2015 date
As this year, Aug 19 & 20 Tithi is Panchami, a few people celebrate on Aug 19, 2015 and others who calculate Tithi for Nag Panchami and sacred thread changing date celebrate on August 20 and Yagnopaveetham or sacred thread changing day on August 28.