When does a Genesis day start

Understanding that the ordinary Scriptural calendar day was reckoned from daybreak to daybreak (or dawn to dawn) is essential for understanding the following:
Creation – Genesis 1,
The monthly and yearly cycle – Exodus 12,
The – Deut. 16,
plus many other scriptural passages, including Hosea 6:1-3, and passages concerning the timing of Messiah’s death and resurrection.

We do not share the presupposition of the traditionalists that the sunset day is correct, but require historical proofs based only on * accurate translation of the original Hebrew, * scientific method, and * sound linguistics, and not circular reasoning from the tradition or authorities.

So when does the creation Genesis day begin?

The literal day is defined in:
Gen. 1:3-5a:
Then the Almighty said ‘Let there be light.’ Then there was light. Then the Almighty saw the light, that it was good. Then the Almighty separated between the light and between the darkness. Then the Almighty called the light ‘day.’

We see here that the literal day is defined as – light, and so it is limited to the time between dawn and dusk. When the separation is complete, the full light is called ‘day,’ and of course logically this ends when the light goes away.

The twenty-four hour calendar day is added onto the definition of the literal day in:

Gen. 1:5b:
And darkness he has called ‘night’: 1) Then there was setting (k1); 2) then there was daybreak (d2); one day. One day is understood as one calendar day, or one twenty-four hour period, which started with the creation of light at the first dawn, and then ended at the next daybreak, ready to start a new day.
The ESV study bible explains:

There was evening and there was morning, the first day. The order – 1) evening, then 2) morning – there is an evening, and then a morning, implying that there is a night-time in between. So the ordinary twenty-four calendar day is timed from one daybreak to the next daybreak. I will break this down more later.