You may have noticed that the passage I have given above does not run concurrently with the previous day's one! This is because we are studying this very difficult, apocalyptic chapter and Jesus' prophecy weaves from His second coming to the destruction of Jerusalem and back again. This is typical of Prophetic messages.
In these verses, Jesus is prophesying the destruction of Jerusalem, some of the awful terror of those days with the siege and the fall of this magnificent city, the city of God. The first thing He tells His listeners is that when this siege comes-and as it occurs less than 40 years after His death, there will be some in the crowd listening who will still be alive then, (also, it is generally accepted that the Gospel of Mark was written before that date and so the readers of this work could be warned)-people ought to flee from Jerusalem to the countryside. Now, generally the opposite would be the reality. When those living in the many villages surrounding Jerusalem heard news of the vast Roman war machine being on its way they would have headed for the security of the walled city. Real faith does the opposite of what is logical sometimes! Many Christian believers survived by heeding Jesus' message.
The phrase 'abomination of desolation' had its origin in the book of Daniel, repeated in the later chapters. Originally, it referred to Antiochus Epiphanes, whom I think I have mentioned previously. He was a Greek leader who tried to stamp out the Jewish religion by invading Jerusalem and offering pig's flesh on the altar. He set up an image of Zeus in the Temple and ordered the Jews to worship it. Jesus thus prophesied that it would be repeated. Caligula, the mad Roman Emperor almost succeeded in setting up an image of himself in the Temple, but died before it took place.
So, in AD 70, Titus and the Roman army captured Jerusalem. They had starved the city into subjection as it refused to surrender. The contemporary historian, Josephus, records that over one million people died from starvation! Only those who took His word and fled to the countryside survived!