About Sandhi Puja:
Sandhi Pooja is a very significant ritual during Navratri Pooja. 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 Pooja is dominant for two Ghatis or approximately lasts for 48 minutes. It is possible that Sandhi Pooja Muhurta occurs at any time of the day and Sandhi Pooja should be done during that time only.
You might also refer the complete Shardiya Navratri Calendar and Durga Puja Calendar.
Sharad Navratri 2019 Dates
Navratri Day 1 / Pratipada
Ghatasthapana, Chandra Darshan, Shailputri Puja
Color of the day – Orange
29th September 2019 Sunday
Navratri Day 2 / Dwitiya
Brahmacharini Puja
Color of the day – White
30th September 2019 Monday
Navratri Day 3 / Tritiya
Sindoor Tritiya, Chandraghanta Puja
Color of the day – Red
1st October 2019 Tuesday
Navratri Day 4 / Chaturthi
Kushmanda Puja, Varad Vinayaka Chauth, Upang Lalita Vrat
Color of the day – Royal Blue
2nd October 2019 Wednesday
Navratri Day 5 / Panchami
Skandamata Puja
Color of the day – Yellow
3rd October 2019 Thursday
Navratri Day 6 / Shashthi
Saraswati Awahan, Katyayani Puja
Color of the day – Green
4th October 2019 Friday
Navratri Day 7 / Saptami
Saraswati Puja, Kalaratri Puja
Color of the day – Grey
5th October 2019 Saturday
Navratri Day 8 / Ashtami
Durga Ashtami, Mahagauri Puja, Sandhi Puja, Maha Navami
Color of the day – Purple
6th October 2019 Sunday
Navratri Day 9 / Navami
Ayudha Puja, Navami Homa, Navratri Parana
Color of the day – Peacock Green
7th October 2019 Monday
Navratri Day 10 / Dashami
Durga Visarjan, Vijayadashami
8th October 2019 Tuesday