Shani Jayanti is marked as birth anniversary of Lord Shani. Shani Jayanti is also known as Shani Amavasya. Lord Shani is son of Lord Suryadev and rules planet Saturn and weekday Saturday. According to Astrology, Shani is referred to as Saturn which is known to have a strong influence upon people's life.
As per Ancient Vedic Texts, Saturn is a Cruel planet. Astrologically, it is said that planet Saturn is a judge of our past deeds. When Saturn is adverse, it causes many problems, accidents, conflicts, poor financial position, sorrow, sadness, depression, poverty etc. Under such circumstances, a Shani Puja or Yantra can bring peace and comfort. People also perform Navgraha Shanti Puja to the best of their abilities on Shani Jayanti to please planet Saturn.
As per Hindu texts, Shani Dev is the son of Lord Surya and Devi Chaaya, the shadow of the wife of Lord Surya, Devi Saranyu. It is said that Devi Sarnyu could not bear the heat and brightness of Lord Surya and left him. She went away for penance and left her Shadow Chaaya to take her place. As Shani Dev was born during the time when Devi Chaaya was in severe penance meditating Lord Shiva, he was born dark. The dark complexion of Lord Shani made Lord Surya doubt over the chastity of Chaaya and he used to insult her. (ref@mpanchang)
It is said that once infuriated by the insults of Lord Surya, Lord Shani casted cruel gaze on him due to which he got burnt and his complexion turned to black. At that time, Lord Shiva healed Lord Surya and unravelled the truth of Chaaya and Lord Shani’s birth. Also, Lord Shiva blessed Lord Shani with greats powers and authority to punish people for their wrong and evil deeds.
" Om Praang Preeng Praung Sah Shanishcharaya Namah "
But the fact is that this slow-moving planet is the planet of Karma. It offers success only to people who have undergone penance, hardships, and struggle and worked in their life through hard work, discipline, and sincere efforts. Whether an individual will be blessed or will be prone to bad luck, depends upon his/her deeds done in the past and the present lives. Lord Shani is just and fair and gives the natives the result of their own Karma. Shani is considered as the Lord of the West
Shani Jayanti has lot of significance of its own in the Indian culture. People strongly believe that by worshipping Lord Saturn, all the hurdles and problems in one’s path are eliminated.