Ganesh Jayanti (Maghi Ganesh Chauth) is observed on Shukla Paksha Chaturthi in Magh month as per all lunar Hindu calendars. The story of Ganesh Jayanti is associated with a righteous King and his queen Ratnavali. The vrat katha goes like this…
Once there was a righteous and judicious King. His queen Ratnavali was wise and virtuous. The couple led a happy and contented life. On one unfortunate day their kingdom was attacked by enemies and both were thrown into the forest.
To get rid of their bad state and to know the solution, they met Markandeya Mahamuni. They explained him everything and wanted to have a solution.
After meditating for a while, Mahamuni Markandeya told them that their worst stage was the result of their sins in previous birth. The king was a hunter in his previous birth and used to observe Ganesh Jayanti vrat. But he stopped observing it later. He became the King in present life due to his merits earned through Sakata Chaturthi vrat observance. As he stopped observing vrat, he has to come across the bad phase.
Markandeya Rishi advised the couple to observe Sakata Chauth vrat to got rid of their sins in previous births. They had successfully observed the Vrata and got back their lost empire, happiness and glory.