Chaitra Navratri is celebrated in March/April and Sharad Navratri is celebrated in September/October. As per Hindu scriptures, Lord Rama worshipped Goddess Durga before defeating Ravana, this story of Rama's Navratri worship before defeating the evil gave rise to Sharad Navratri. Maa Durga later killed Mahishasura after a nine-day battle and this occurred in the Hindu lunar month of Chaitra.