Two times are given in Ezekiel 4, indicating two separate prophetic periods. Both periods are presented in days which represent years, and the years of their prophecies are 390 years and 40 years. Both prophecies are linked to sins: the sins of Israel and of Judah, respectively. Those sins are what mark the beginning points of the prophecies. The end point of both is what is described throughout the chapter--the siege and breakup of Jerusalem. Of special focus in Jerusalem is the Temple. Whereas the actual siege may last for an indefinite period of time, the Temple's destruction clearly marks the endpoint of the prophecies. Twice, the Temple was destroyed; and these twin prophecies predict the times for both destructions of the Temple.
Understanding the Prophetic Symbols
The symbols of the prophecy are the key to understanding it.
The context clearly indicates a siege;
The city involved is clearly Jerusalem;
The prophecy is given for "iniquity" (both of Israel and of Judah);
The prophecy for Israel is given before that of Judah, indicating their order; and
The iniquities are not equal, as indicated by Ezekiel's left versus right sides.
The Iniquity of Israel
The iniquity of Israel is so often mentioned throughout the books of the kings as to be unmistakable.
1Ki 14:16 And he shall give Israel up because of the sins of
Jeroboam, who did sin, and who made Israel to sin.
1Ki 21:22 And will make thine house like the house of Jeroboam the
son of Nebat, and like the house of Baasha the son of Ahijah, for
the provocation wherewith thou hast provoked me to anger, and made
Israel to sin.
1Ki 22:52 And he did evil in the sight of the LORD, and walked in the
way of his father, and in the way of his mother, and in the way of
Jeroboam the son of Nebat, who made Israel to sin:
2Ki 10:29 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.
2Ki 23:15 Moreover the altar that was at Bethel, and the high place
which Jeroboam the son of Nebat, who made Israel to sin, had
made, both that altar and the high place he brake down, and burned the
high place, and stamped it small to powder, and burned the grove.
(See also 1 Kings 15:26, 34; 1 Kings 16:2, 19, 26; 2 Kings 3:3; 2 Kings 10:31; 2 Kings 13:2; 2 Kings 14:24; and 2 Kings 15:8-9, 24, 28.)
It is plain to see that Jeroboam caused Israel to sin, and that this was a significant event. What did he do? He built the golden calves at Dan and at Bethel and caused the people to worship them instead of going to Jerusalem to worship God. He was afraid they would return to serving king Rehoboam, instead of himself, if they returned to Jerusalem for worship as had been their custom.
The fact that they had turned away from the worship of God in Jerusalem, and had turned away from God's temple, wonderfully built by King Solomon to the glory and honor of God, is what brought God to allow the destruction of that beautiful temple 390 years later, as indicated in the prophecy. The years were not years of punishment, they were years of probation before the punishment would come.
The Iniquity of Judah
However, as the Bible places greater significance to the right side than to the left, the prophecy indicates that Judah's sin would be greater yet. In spite of this fact, much less appears to be said about it--in the Old Testament, at least. The one text specifically mentioning it seems ominous:
"The sin of Judah is written with a pen of iron, and with the point of
a diamond: it is graven upon the table of their heart, and upon the
horns of your altars" (Jeremiah 17:1)
When one thinks of a "pen of iron," what comes to mind?
In Jesus' day, the remnants of the 10 tribes (the Northern Kingdom / Israel) had become the hated Samaritans. They had intermarried with the surrounding nations, and, thinking them impure, the Jews (Judah) would not even permit them to enter the temple. Thus it was Judah for whom Christ labored.
And it was Judah who rejected Christ. The "pen of iron" is a fitting description for the nails which pierced Christ; and the "point of a diamond" is a fitting symbol for the spear that would pierce his side.
Just forty years later, the second temple was also destroyed. Not only had Judah rejected the true worship of God; they had murdered him. Their probationary time was much less, and their punishment came more swiftly and in greater severity.
Thus, Ezekiel's prophecy foretold both apostasies, and both destructions of the temple that would come on account of them.
At the end of the 390-year prophecy, Jerusalem is broken up and Solomon's temple is destroyed. Judah's sin happens much later in time, is much greater in significance, and less probation is granted afterward before the temple, the second one, is again destroyed, along with those who had taken refuge inside. It was 40 years after Christ's crucifixion that Jerusalem was broken up and the temple destroyed. So the 40-year prophecy begins at the murder of Christ and culminates with the destruction of the Temple and of the Jews in Jerusalem.
The 40-year portion of the prophecy in Ezekiel 4 is unrelated to the 70-year prophecy of Jeremiah, but stands as its own prophecy which is fulfilled around 600 years later.