01What Sharad Navratri is
Sharad Navratri, also called Shardiya Navratri, is the autumn Navratri, the nine nights of the goddess from Shukla Pratipada of Ashwin, after the monsoon. It is the largest of the four Navratris of the year and the one most people mean by the word. Each day honours one of the nine forms of Durga. It takes many regional shapes: Durga Puja in Bengal, Assam and Odisha, garba and dandiya in Gujarat, Golu displays of dolls in Tamil Nadu and Karnataka, and Ramlila across the north. The tenth day is Vijayadashami, Dussehra.
02The story told of it
The tradition tells of two victories in these nights. The first is the goddess's: in the Devi Mahatmya, Durga, formed from the united power of the gods, faces Mahishasura, the buffalo asura no god could overcome, and defeats him, which is why she is called Mahishasuramardini. Bengal's Durga Puja also honours her as a daughter coming home to her parents for these days. The second is Rama's: an account kept in the east says Rama worshipped the goddess out of season, in autumn, before his battle with Ravana, which is why this Navratri leads into Dussehra, the day of his victory.
03How it is kept
Ghatasthapana opens the nine nights: on Pratipada a kalash is installed over sown barley, in the first third of the day while Pratipada lasts, or at Abhijit when it does not, and an akhand jyoti is often kept burning to the end. This page lists each day by its tithi at sunrise, with the form of Durga given to that tithi: Shailaputri, Brahmacharini, Chandraghanta, Kushmanda, Skandamata, Katyayani, Kalaratri, Mahagauri and Siddhidatri. When one tithi holds two sunrises the Navratri runs ten days, and when one is skipped it runs eight. Fasting, kanya pujan on Ashtami or Navami, and the barley shoots carried to the water close it.
04How the day is chosen
Navratri begins on the day Pratipada is current at sunrise, and each day after it is listed by the tithi at that day's sunrise. A tithi current at two sunrises adds a day; one that touches no sunrise takes one away.
05Sharad Navratri in other years