I look at it like this: Jesus said 3 days and 3 nights. If He had said just 3 days, we could assume parts of days, but He explicitly stated 3 days and 3 nights.
Yes He did. Now think about it just a little more closely. Hebrews reason time as evening to morning thus if meant as literal 12 hour segments He would have said 3 nights and 3 days.
So besides the fact that ten times the word explicitly says that the resurrection would take place on the "third day" (Mat.16:21; 17:23; 20:19; Mark 9:31; 10:34, Luke 9:22; 13:32; 18:33; 24:7,46), take a look at another example (there are more).
See Esther 4
15 Then Esther bade them return Mordecai this answer,
16 Go, gather together all the Jews that are present in Shushan, and fast ye for me, and neither eat nor drink three days, night or day: I also and my maidens will fast likewise; and so will I go in unto the king, which is not according to the law: and if I perish, I perish. (thus 3 days both day and night would mean a full 72 hours later according to your reasoning...but read on)
17 So Mordecai went his way, and did according to all that Esther had commanded him.
Now 5
5 Now it came to pass on the third day that Esther put on her royal apparel, and stood in the inner court of the king's house, over against the king's house: and the king sat upon his royal throne in the royal house, over against the gate of the house.
On the third day....Hmmm? Shall I show you more?
Yes He did. Now think about it just a little more closely. Hebrews reason time as evening to morning thus if meant as literal 12 hour segments He would have said 3 nights and 3 days.
So besides the fact that ten times the word explicitly says that the resurrection would take place on the "third day" (Mat.16:21; 17:23; 20:19; Mark 9:31; 10:34, Luke 9:22; 13:32; 18:33; 24:7,46), take a look at another example (there are more).
See Esther 4
15 Then Esther bade them return Mordecai this answer,
16 Go, gather together all the Jews that are present in Shushan, and fast ye for me, and neither eat nor drink three days, night or day: I also and my maidens will fast likewise; and so will I go in unto the king, which is not according to the law: and if I perish, I perish. (thus 3 days both day and night would mean a full 72 hours later according to your reasoning...but read on)
17 So Mordecai went his way, and did according to all that Esther had commanded him.
Now 5
5 Now it came to pass on the third day that Esther put on her royal apparel, and stood in the inner court of the king's house, over against the king's house: and the king sat upon his royal throne in the royal house, over against the gate of the house.
On the third day....Hmmm? Shall I show you more?