The third hour (around 9 AM or so) on the day Jesus was crucified is irrelevant when calculating the day, since he was still alive at that time. His prophecy was...
For just as Jonah was three days and three nights in the belly of the great fish, so will the Son of Man be three days and three nights in the heart of the earth. (Matt. 12:40 ESV)
Jesus wasn't "in the heart of the earth" at the third hour. In fact, he would still be alive for another 6 hours after that. After that, quite a lot had to happen, not all of which is recorded in the Bible, before Jesus was "in the heart of the earth".
- Somebody (probably Joseph of Arimathea) went to Pilate and asked for permission to take down the body
- A soldier went to Calvary to make sure Jesus was dead (Maybe somebody who's been there can tell us how far that is)
- The soldier came back to Pilate and told him Jesus was dead
- Pilate gave his permission
- Joseph (or whoever else talked to Pilate) goes back up to Calvary
- The group make plans on who is to provide and do what
- Some people take the body down, while others go get spices and other necessities
- The body is carried to the tomb
- The spices and other things are brought to the tomb
- The body is cleansed
- The body is anointed and wrapped
- The body is put in the tomb
- A two ton stone is rolled over the mouth of the tomb
Each of these things took time. Jesus could not have been "in the heart of the earth" until at most 30-60 minutes before sunset. Are you really going to count that as a whole day? If you started out in the evening and drove for half an hour to get somewhere, would you say it had taken you all day?
The TOG