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: Monday 8th October 2029
Pratipada
Ghatasthapana
Shailputri Puja
Navratri color of the day – White
Navratri Day 2: Tuesday 9th October 2029
Dwitiya
Chandra Darshan
Brahmacharini Puja
Navratri color of the day – Red
Navratri Day 3: Wednesday 10th October 2029
Tritiya
Sindoor Tritiya
Chandraghanta Puja
Varad Vinayaka Chauth
Navratri color of the day – Royal Blue
Navratri Day 4: Thursday 11th October 2029
Chaturthi
Kushmanda Puja
Upang Lalita Vrat
Navratri color of the day – Yellow
Navratri Day 5: Friday 12th October 2029
Panchami
Skandamata Puja
Katyayani Puja
Navratri color of the day – Green
Navratri Day 6: Saturday 13th October 2029
Saptami
Saraswati Awahan
Kalaratri Puja
Navratri color of the day – Grey
Navratri Day 7: Sunday 14th October 2029
Ashtami
Saraswati Puja
Durga Ashtami
Mahagauri Puja
Sandhi Puja
Navratri color of the day – Orange
Navratri Day 8: Monday 15th October 2029
Navami
Maha Navami
Ayudha Puja, Navami Homa
Navratri color of the day – Peacock Green
Navratri Day 9: Tuesday 16th October 2029
Dashami
Navratri Parana
Durga Visarjan, Vijayadashami
Navratri color of the day – Pink