“It was the third hour when they crucified him.” This was when the act of crucifixion started.
Normally those who were crucified were left on the crosses, according to some commentaries as long as nine days. Jesus suffered pain, thirst, torture, insects, crowd insults…it was supreme torture and humiliation.

There were many, many prophecies fulfilled in the crucifixion. You can read all about them in Psalm 22. It reads like an eyewitness account.
Mark 15:34
And at the ninth hour Jesus cried out in a loud voice, "Eloi, Eloi, lama sabachthani?"-- which means, "My God, my God, why have you forsaken me?"

Ps 22:1
My God, my God, why have you forsaken me? Why are you so far from saving me, so far from the words of my groaning?

Psalm 22 reads like an eyewitness account. When Jesus spoke these words from the cross, "My God, my God, why have you forsaken me?", He was telling those who were listening to look at Psalm 22.

“Father into your hands I commit my spirit.”
“..they did not break any bones.”
The breaking of bones was a way to hasten death. When they pierced Jesus’ side with a spear bringing a flow of blood and water it was proof of death. There was no need to break His bones.

For details concerning the trials and a physician’s view of the crucifixion see
http://www.philandpatti.com/abiblicalviewofholyweek
(Part 2 and Part 3)

Crucified bodies became the property of the state and were dumped in the garbage pile at Gehenna. Only by permission could the bodies be taken for proper burial. Joseph of Arimathea was rich, had great influence and many connections. He was also Mary’s great uncle, possibly a kinsman redeemer. This gave him legal standing to go to the Roman authorities and claim the body. He and Nicodemus were both members of the Sanhedrin.

Jesus was taken from the cross; His body was hurriedly anointed with some spices that Nicodemus had brought. The preparation that Joseph and Nicodemus did was an intended temporary measure.

They quickly placed Jesus in Joseph’s tomb before the Sabbath began at 6:00 pm. When
unembalmed bodies were placed in tombs, spices, ointments and wrappings were temporarily put in place. Three days later the stone would be rolled back and people could inspect the body to insure that the person was really dead and not just comatose. (the odor after three days would be more than enough to indicate death.) It was and still is customary for a permanent preparation to be made three days after death. After the permanent preparations are taken care of the tomb is resealed and about one year later it is reopened. The bones are then gathered and placed in ossuaries. The tomb can then be reused for another year with another body. This is why the women were in no hurry to go to the tomb before three days had expired. As another example of how this process worked we can read about what happened with Lazarus. Jesus planned the delay of four days to raise Lazarus. That is so there would be no doubt that Lazarus was indeed dead. The body would have been inspected and permanently prepared a day earlier, when three days had passed, the normal custom of the day.

It is only through learning of the burial customs of the day that we understand a great truth. Jesus was in the tomb three full days and three full nights validating proof of His messiahship, His only sign.
Mat 12:38-40 Then certain of the scribes and Pharisees answered him, saying, Teacher, we would see a sign from thee. But he answered and said unto them, An evil and adulterous generation seeketh after a sign; and there shall no sign be given it but the sign of Jonah the prophet: for as Jonah was three days and three nights in the belly of the whale; so shall the Son of man be three days and three nights in the heart of the earth.

Jesus' validating proof of three days and three nights matters for only one reason. When there appears to be a conflict between what Scripture says and what tradition says, Christians should always be prepared to give an answer from the Bible to clear up any confusion.