Revathi is the 27th Nakshatra or birth stars in Hindu Astrology. Ratha Saptami is an auspicious day dedicated to Bhagwan Surya, the sun god in Hinduism, in Magh month. When Revathi Nakshatra and Ratha Saptami day falls on the same day the Shukla Paksha of Magh month, it is considered highly auspicious.
When such a rare occurrence happens in Hindu calendar, it is known as Padmaka Yoga. The belief is that the day is then equal to Thousand Surya Grahana Maha Parvakala.
If Ratha Saptami falls on Sunday, it is termed as Vijaya Yoga and this is considered highly auspicious to propitiate Surya.
If the Rashi or Moon sign as per Hindu astrology changes on Ratha Saptami day, then the day is ideal for performing tarpana, Shradh, snan (holy bath) and meditation.