How does Mark's Gospel mark the final hours in the life of Jesus Mark's Gospel makes frequent use of chiastic and parallel structures, and there appears to be an important structure in chapters 14 and 15, marking off time intervals in the 24 hours from the Last Supper to Jesus' burial by Joseph of Arimathea. 

How are those time intervals defined in Mark?
John Shelby Spong describes the structure quite succinctly in Jesus for the NonReligious, pages 101-4.  He says Mark organised the first narrative account of the death of Jesus in a twenty-four hour cycle, neatly divided into eight three-hour segments. A summary of Bishop Spong's explanation follows: 


Mark started the story "when it was evening" (Mark 14:17). In this ancient
world, that would mean when the sun went down at 6 pm. [The ancients divided the daylight hours into exactly 12 hours of variable length, instead of a variable number of hours of fixed length.]
Mark knew that the duration of the Passover meal was three hours and that it concluded with the singing of a hymn.  So at the end of his segment he noted, "And when they had sung a hymn they went out to the Mount of Olives" (14:26). It was obviously about 9 p.m.
Mark then has Jesus and the disciples go to the Garden of
Gethsemane, where his closest disciples, Peter, James and John, were
not able to remain awake. "Could you not watch one hour?” (14:77)
Jesus asked.  The process was repeated two more times.  The
disciples could not watch one, two or three hours.  It was now midnight.
The act of betrayal, the darkest deed in human history, came next,
occurring at the stroke of midnight.
Jesus was led away for a trial before the high priest and other
senior priests and elders. They then judged him, on the basis of his messianic claim, to be worthy of death.  It was 3:00 a.m.
The watch of the night between 3 am and 6 am was called cockcrow. Mark now inserted his account of Peter's threefold denial of Jesus (14:66-72), once each hour until the cock crowed, marking the end of that phase of the night.  It was 6 a.m.
"As soon as it was morning" (15:1), which would be 6 am, Jesus was
led by the chief priests, scribes and elders to Pontius Pilate for
judgement.
Mark told his readers, " It was the third hour" or 9 am “when they
crucified him" (15:25).
When "the sixth hour had come" (15:33) – 12 noon – darkness covered the whole earth for 3 hours, at which time Jesus said "My God, my God, why hast thou forsaken me?" (15:34).
Jesus was buried in the final period from 3 to 6 pm, before the sun went down and the Sabbath began.