I have read this thread twice, and I am still not sure that I understand the question. Are you asking what calendar day marks the beginning of the year from God's perspective, or are you asking something else?
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Yes, that is correct
My insight: I said earlier
Starting from creation God said it was good and very good. Meaning it was exactly the way He planned it. Another way of saying this it was a time without sin. So, what in the scriptures denote no sin for 7 days?
I see creation being represented by the Feast of Unleavened Bread. Lev 23:5-6. A springtime event.
The sixth day, the day Adam was made, was the timing of the original Passover. When they sinned that day they covered themselves with fig leaves which didnt qualify for the covering of sin. It took a blood sacrifice to suffice as a temporary covering in which he made clothing from animals till the Lord was crucified as the final sacrifice on the sixth day of the week exactly 4000 years lately.
The lord's timing was perfect--Crucified on Passover according to the plan set forth from creation.
Malachi 4: 2 But for you who fear my name the sun of righteousness shall rise, with healing in its wings. You shall go forth leaping like calves from the stall
Calves represent those who were raised on the Passover weekend.
Healing was the Resurrection
Sun of Righteousness is the lord Jesus ( notice sun not son ) telling his exact timing of appearing 4000 years from creation on Passover
as the Sun was made on the fourth day.
A Day to the Lord is a thousand years--4th day =4000 years--What a perfect God and Savior we have