Hi rstrats,
First, (in case you did not know) the Jewish day ran from sundown to sundown. (approx 6pm to 6pm)
Luke 23:44-46 shows Jesus died about 3 pm. Luke 23:54-56a shows that this was the day before Sabbath. They bury him before sundown.
Luke 23:56b they rest on the Sabbath.
Luke 24:1-3 at early dawn the next day they go to tomb but find it empty. presumably Jesus has been raised.
Translating this into our days, and using Friday as the day of death:
Fri, 3pm Jesus dies and buried before sundown.
Fri, 6pm to Sat 6pm is Sabbath, nothing happens this day.
Sat 6pm to Sun 6pm is first day of the week. Jesus raised sometime before "early dawn" Sunday morning.
So, supposing a Sun 6am resurrection, Jesus is dead from Fri 3pm to Sun 6am, or roughly 39 hours. But by Semitic time reckoning it is 3 days (actually, to us, parts of 3 days). He is dead about 3 hours Friday, 24 hours Saturday, and perhaps 12 hours Sunday.
Here is the Luke account at Lumina (for easy reference).
As I pointed out in an earlier post, the "three days and three nights" statement of Mt 12:40 may have been an attempt to create an equivalence in the hearing of his listeners between Jesus' coming experience and with Jonah's past experience in the fish as stated at Jonah 1:17. With our modern time keeping and dependence in life on precision in our time keeping, this appears to us to be an egregious mis-counting of time. But to Jesus' listeners (with not a single watch or calendar among them) they would not have batted an eye over it. Nor is there any record in the gospels or Acts of any later dispute about it. To me, the seeming discrepancy is more due to cultural differences between us moderns and the ANE.