Surya Jayanti, also known as Ratha Saptami or Saur Saptami or Achala Sapthami, is observed on Magh Shukla Saptami day. In 2018, Surya Jayanti date is January 24.
This festival is popularly celebrated as Ratha Saptami and also marks the birthday of Lord Surya. Surya Bhagwan was born to sage Kashyapa and his wife Aditi on this day.
Devotees believe that Magh month is very auspicious and mainly dedicated to Surya Bhagwan and Lord Shiva. Surya Jayanthi puja is performed throughout India. In Orissa, Konark Surya temple is the place where jubilant celebrations will be held.
According to Mahabharata, Bhishma got the salvation (death) on the day after Surya Jayanthi i.e. on Bhishma Ashtami. Surya Bhagwan is also considered as the God of health in Hinduism hence he is worshipped for better health on Surya Jayanthi day.