I had heard about some debates on whether Jesus was crucified on a Thursday or on a Friday. Tradition teaches that it was a Friday, and we see that tradition in the day called Good Friday. Jesus did say that He would be buried for three days and nights. Those who propose He was crucified on a Thursday say that He could not have been buried for three nights if He had been crucified on a Friday and had arisen on Sunday morning. However, I know that the Jews counted part of a day as a whole day. If Jesus were crucified on Thursday, He would have been buried for four days because Thursday, Friday, Saturday, and Sunday would have been counted as days. However, a Thursday’s crucifixion does allow for three nights (Thursday, Friday, and Saturday night). A Friday’s crucifixion does not seem to allow for three nights. Please resolve this issue for me.
It seems you have this issue pretty much figured out for yourself. There is debate among scholars and among faithful conservative Christians over this, but I believe most likely the correct answer is that for the Jews "three days and three nights" was an expression which literally meant any part of three twenty-four-hour days. Friday is day 1, Saturday is day 2 and Sunday is day 3, therefore the Jews would say "three days and three nights." This Jewish idiom explains the biblical statements.
Now, if we take a Western say of saying things (which does not seem appropriate in my opinion, as the authors were Jewish Near Easterners), then Jesus must have been crucified on Thursday, which means he was dead for part of Thursday, part of Sunday, all of Friday and all of Saturday, which, by the clock, is three days and three nights. Because this is not how the Jews reckoned time, I do not think it is the solution. Whether of not Jesus was crucified on Friday is a somewhat open question. Of course tradition says it was a Friday. Then you have to look at the year as Passover moves around to different days. If you look for a year when the Passover fell on a Saturday, and therefore Jesus was crucified on a Friday, this works for the year AD 29, and all the biblical statements work for a Friday crucifixion and a Sunday resurrection.