Sandhi Puja is a very significant ritual during Navratri Puja. It is performed at the point when Ashtami Tithi ends and Navami Tithi begins. This is believed to be the moment when Devi Chamunda appeared to kill the demons Chanda and Munda.
Sandhi Puja is dominant for two Ghatis or approximately lasts for 48 minutes. It is possible that Sandhi Puja Muhurta occurs at any time of the day and Sandhi Puja should be done during that time only.
You might also refer the complete Shardiya Navratri Calendar and Durga Puja Calendar.
Navratri Day 1: Saturday 28th September 2030
Pratipada
Ghatasthapana
Shailputri Puja
Navratri color of the day – Grey
Navratri Day 2: Sunday 29th September 2030
Dwitiya
Chandra Darshan
Brahmacharini Puja
Navratri color of the day – Orange
Navratri Day 3: Monday 30th September 2030
Tritiya
Sindoor Tritiya
Chandraghanta Puja
Kushmanda Puja
Varad Vinayaka Chauth
Navratri color of the day – White
Navratri Day 4: Tuesday 1st October 2030
Panchami
Upang Lalita Vrat
Skandamata Puja
Navratri color of the day – Red
Navratri Day 5: Wednesday 2nd October 2030
Shashthi
Katyayani Puja
Navratri color of the day – Royal Blue
Navratri Day 6: Thursday 3rd October 2030
Saptami
Saraswati Awahan
Kalaratri Puja
Navratri color of the day – Yellow
Navratri Day 7: Friday 4th October 2030
Ashtami
Saraswati Puja
Durga Ashtami
Mahagauri Puja
Sandhi Puja
Navratri color of the day – Green
Navratri Day 8: Saturday 5th October 2030
Navami
Maha Navami
Ayudha Puja, Navami Homa
Navratri color of the day – Peacock Green
Navratri Day 9: Sunday 6th October 2030
Dashami
Navratri Parana
Durga Visarjan, Vijayadashami
Navratri color of the day – Purple