Those listening to him that day would have known about the destruction of the first temple and the pain and disruption of the exile that the destruction had signaled. Those would have read the words that the prophets had used to call the people to repentance and change and the accusations and sorrow that followed when they did not.
They responded to his announcement by asking "How will we know when this is going to happen?"
Jesus cautioned them not to be misled by some who would claim to be coming in his name. Still good advice. Then he told them what signs would foretell the end: Wars and insurrections, natural disasters, and great signs from heaven.
With help from Allen & Williamson's Preaching the Gospels, here are several texts that would be useful for background reading:
God destroyed the first temple because of Israel's unfaithfulness, Jeremiah 7:1-14
Signs of tribulation, 2 Chronicles 15:5-6; Daniel 11:20-44.
Elements of nature--earthquakes, famines, plagues, and astrological signals, Haggai 2:6; Zechariah 14:5