Rath Saptami vrat or Ratha Saptami puja is observed on Magh Shukla Saptami, the seventh day in the month of Magh. In 2017, Rath Saptami date is February 3. Ratha Saptami vrata katha or story of Rath Saptami is connected with King Yashovarma.
Once a King called Yashovarma was ruling the Kamboj Empire. He was extremely religious and his people were living happily and were praising his ruling. But he had no children to rule the country after him. He had become old. He worshipped God to give him a son. God was impressed with his prayers and given him a son who was very sick. The king was unhappy due to his sons sickness.
A Muni or Saint called Vinit came to the king and told him that his sickness is because of his sins he had done in his previous birth. As the remedy to the kings sickness he advised the king to make his son to observe vow of Ratha Saptami. Kings son performed the puja on Ratha Saptami and became healthy to rule his people without any sufferings.
Ratha Saptami is also known as Surya Jayanthi. It is believed that on this day, Surya Bhagwan was born. Surya Bhagwan is worshipped on Surya Jayanti or Rath Saptami for better health and prosperity of their family. This festival is also called as Maha Saptami, Jaya Saptami or Jayanthi Saptami.
Other major festivals dedicated to Surya Bhagwan are Bhanu Saptami or Vivasvat Saptami (Ashada Shukla Saptami), Mitra Saptami (Margasira Sapthami), Surya Sashti (Bhadrapad Shukla Sashti), and Chhat Puja or Dala Chhat Vrat.