@rstrats
From my previous (2018) post #179:
* In Mark 8:31 Jesus says "after three days”
Mark was the first gospel written
* In Matthew 12:40 it's written as "three days and three nights"
* In John 2.19 it's "three days"
* In Luke 13:32 and 24:46 it's written "on the third day", as it is too in Matthew 16:21; 17:23 and 20:19.
So in only one of several passages is the "three nights" added -- obviously as a reference to Jonah -- and as I am quite happy to take the consensus, it doesn't seem to trouble me much. There are other contradictory New Testament passages that have far more serious implications for a literal reading.
They had to break the legs of the crucified, because it was not allowed for the crucifixion to continue on the sabbath. That would be the Saturday, but starting at sundown on Friday -- which is the reason for assuming a sixth day crucifixion?
I understand a Sunday resurrection excludes a third night as in Matthew 12:40. But as several other passages (above) do not mention a third night, it seems reasonable for traditional Christian liturgy to work with a sixth day crucifixion?
But who knows?
Which I realise is off topic, and will do nothing to satisfy your query, but it's the best I can do this year.
Best wishes to you this Easter