Ezekiel 4 Prophecy

“Now, son of man, take a block of clay, put it in front of you and draw the city of Jerusalem on it. Then lay siege to it: Erect siege works against it, build a ramp up to it, set up camps against it and put battering rams around it. Then take an iron pan, place it as an iron wall between you and the city and turn your face toward it. It will be under siege, and you shall besiege it. This will be a sign to the people of Israel. “Then lie on your left side and put the sin of the people of Israel upon yourself. You are to bear their sin for the number of days you lie on your side. I have assigned you the same number of days as the years of their sin. So for 390 days you will bear the sin of the people of Israel. “After you have finished this, lie down again, this time on your right side, and bear the sin of the people of Judah. I have assigned you 40 days, a day for each year. Turn your face toward the siege of Jerusalem and with bared arm prophesy against her. I will tie you up with ropes so that you cannot turn from one side to the other until you have finished the days of your siege. Ezek. 4:1-8

The sins of Jeroboam:
1) And he shall give Israel up because of the sins of Jeroboam, who did sin, and who made Israel to sin1 Kings 14:16 
2) Because of the sins of Jeroboam which he sinned, and which he made Israel sin, by his provocation wherewith he provoked the LORD God of Israel to anger. 1 Kings 15:30 
3) Howbeit from the sins of Jeroboam the son of Nebat, who made Israel to sin, Jehu departed not from after them, to wit, the golden calves that were in Bethel, and that were in Dan...But Jehu took no heed to walk in the law of the LORD God of Israel with all his heart: for he departed not from the sins of Jeroboam, which made Israel to sin
2 Kings 10:29, 31 
4) And he {Jeroboam, son of Jehoash} did that which was evil in the sight of the LORD: he departed not from all the sins of Jeroboam the son of Nebat, who made Israel to sin
2 Kings 14:24 
5) And he {Menahem} did that which was evil in the sight of the LORD: he departed not all his days from the sins of Jeroboam the son of Nebat, who made Israel to sin
2 Kings 15:18 

Clearly Israel's sin began with Jeroboam. This is the proper starting point for Ezekiel's prophecy which is in year 949bc.

What was Jeroboam's sin?
Jeroboam thought to himself, “The kingdom will now likely revert to the house of David. If these people go up to offer sacrifices at the temple of the Lord in Jerusalem, they will again give their allegiance to their lord, Rehoboam king of Judah. They will kill me and return to King Rehoboam.” After seeking advice, the king made two golden calves. He said to the people, “It is too much for you to go up to Jerusalem. Here are your gods, Israel, who brought you up out of Egypt.” One he set up in Bethel, and the other in Dan. And this thing became a sin; the people came to worship the one at Bethel and went as far as Dan to worship the other. Jeroboam built shrines on high places and appointed priests from all sorts of people, even though they were not Levites. He instituted a festival on the fifteenth day of the eighth month, like the festival held in Judah, and offered sacrifices on the altar. This he did in Bethel, sacrificing to the calves he had made. And at Bethel he also installed priests at the high places he had made. On the fifteenth day of the eighth month, a month of his own choosing, he offered sacrifices on the altar he had built at Bethel. So he instituted the festival for the Israelites and went up to the altar to make offerings. 1 Kings 12:26-33

Jeroboam made Israel worship other gods and celebrate festivals similar to that of Judah's Feast of Tabernacles on the 15th day of the 7th month, only he chose a month of his own choosing and made it the 15th day of the 8th month. And he forbid the Israelites to go up to the temple in Jerusalem, the place God had chosen for his presence. God had mercy on the Israelites for 390 years, after which he destroyed the Temple and sent them into exile. The destruction of the 1st temple occurred in 586bc, exactly 390 years after Jeroboam's sin. 
Destruction of the 1st Temple - 949bc – 390 = 586bc (FULFILLED)

Judah's sins were less than Israel's the first go around. They had a few faithful kings, but they also had their unfaithful kings just like all of Israel's kings were. Judah also fell into the same idolatry and disobedience. But Judah was shown more mercy by God by allowing them further time to repent until they were exiled.

Now the second part of Ezekiel's prophecy predicts the destruction of the 2nd temple. This time it is due to the sins of Judah. Judah's sin is so bad that God only has mercy on them for 40 years. What was Judah's sin? Judah denied the Messiah at his 1st coming, and not only that, they killed him. 

So Israel rejected the kings whom God had appointed, Judah rejected the King of kings. Israel turned away from God to worship idols, Judah turned away from God to worship pride and tradition. Israel neglected to follow God, Judah murdered Him.
Destruction of the 2nd Temple 31ad + 40 = 70ad (FULFILLED)