I am from Durban, South Africa and I am a bit confused on which day (31 Oct 2024 or 1 Nov 2024) is the main day of Diwali observed (when Lakshmi Puja is conducted). Here is the breakdown of the days according to the Drikpanchang website for my location:
On 31st October: Chaturdashi will prevail up until 12:22 p.m. and thereafter Amavasya prevails until 14:46 p.m on the 1st of November. Besides that, the Swati Nakshatra will be present from 21:15 p.m on the 31st October to 00.02 a.m on 2nd November.
So we are dealing with "mixed" Amavasyas here, which the one on 31st October is referred to as Purva-Amavasya or Sinivali and the one on the 1st of November is called Kuhu or Uttara-Amavasya. The general rule is that the tithi at sunrise is the tithi for the day, hence that will result in Amavasya falling on the 1st of November. According to the Vaishnava Calendar https://www.vaisnavacalendar.info/calendars/2024/Durban%20[South%20Africa].txt, this is indeed the case. However, the major Hindu body in the country stated that Diwali is observed on 31st October 2024.
I can see the point of view of celebrating Diwali on 31st October as Amavasya is present at the night on that day during Pradosh Kaal (18:17 to 20:26). However, Swati Nakshatra is not present during this time.
My question is how is the date for Diwali (falling on Kartik Amavasya) determined according to scripture?