Navratri is a nine days festival dedicated to Goddess Durga. Navratri is a Sanskrit word which literally means nine nights. During these nine nights and ten days, Goddess Durga is worshipped in 9 different forms, known as Navdurga. The tenth day is celebrated as Vijayadashami .
It starts soon after the Mahalaya Amavasya (the New Moon night that marks the end of the Pitru Paksha, a fortnight devoted to the deceased ancestors)
Goddess Durga is worshipped by devotees with four Navratri fasts, every year. The four Navratri fasts are named after the Hindu seasons/months they fall in — Magha (Winter), Chaitra (Spring), Ashadha (Monsoon), and Sharad (Autumn). Of them, Sharad Navratri is considered to be the most prominent. 
This is also known as Shardiya Navratri. 
In West Bengal Navratri is celebrated as Durga Puja.
During the nine days of Navratri, devotees worship nine avatars of Goddess Durga, namely Shailaputri, Brahmacharini, Chandraghanta, Kushmanda, Skanda Mata, Katyayani, Kalaratri, Mahagauri, and Siddhidatri. On the eighth day, also known as Ashtami, and the ninth day, called Navami, devotees of Maa Durga invite young girls for Devi Prasad and Kanya Pujan.  

October 7: Pratipada 

October 8: Dwitiya 

October 9: Tritiya and Chaturthi 

October 10: Panchami 

October 11: Shashti 

October 12: Saptami 

October 13: Ashtami 

October 14: Navami 

October 15: Dashami 

Ashwin Ghatasthapana on Thursday, October 7, 2021 

Ghatasthapana Muhurat - 06:17 to 07:07 

Duration - 00 Hours 50 Mins 

Ghatasthapana Abhijit Muhurat - 11:45 to 12:32 

Duration - 00 Hours 47 Mins