That is the traditional way that the Book of Daniel has been interpreted for hundreds of years, but we must remember that Daniel was told to seal up the Book until the end times. That means that all those interpretations, especially those regarding the counting of the days at the end of the Book, if they were not rendered within the actual counts of 1,290 and/or 1,335 should be disregarded.
The actual basis for this rendering is based upon my being born into a family of kings. My three older brothers became the first three kings of Persia (Daniel 11:2), our common sire becoming the fourth. I am the king of Daniel 11:3. I have known those four kings since I was birthed on June 25, 1956 A.D.
The first king of Persia however put to death the fourth king. This assault began as early as October 1, 1955 A.D. when my mother at the time was no more than six days into term with me in her womb. He shot her twice, and then that fourth king, her husband, four times. I was told he also stole the car that evening. That fourth king died in 2000 A.D, his wife, my mother, died in 2013 A.D. My oldest brother, at least, had put them to death.
Later (post October 1, 1955 A.D.), after years of conflict as recorded in the north/south descriptions, it was put to me as a test of my sainthood to put me under great duress with the same weapon that had been used. Somehow, the second king of Persia became a further victim of assaults, eventually being involved in an automobile collision with serious sustained injuries. Occurring on a Monday, by Thursday he was basically mentally incompetent, yet he hung on for forty days, much like the Fast which the Church now embraces during Lent, remembering Our Lord's Fast in the wilderness.
Because of 16th century French prophecy, I was capable of interpreting translations that foretold that one day of those three original kings, that only two would remain, at some point in time. This became the basis for my analysis, and the prophecy included a time frame that those remaining two would keep a peace. Being as I cannot rule, if you read Daniel 11:4, you will see that, it became obvious to me what those words meant. Specifically, that when their peace would fail, there would be no rule, in essence, anarchy, especially as regards the Book of Daniel because these were some of the last kings foretold. This is in alignment with all prophecy concerning antichrist and its wreaking of havoc. It parallels the post WWII visitations of the Lady of the Nations. And the counting of the days according to the death of a Brother falls on major Feast Days of Our Lord. The evidence is overwhelming.
I have many war stories about the conflict written, most of it fulfilled, in Chapter 11. I can go into detail, but this is not really about me, it is about the fact that the Book, once sealed, is now unsealed. I did not get this straight until after the 850th day was already past.
I have begun to share the count with sites to which I have been in the past. Earlier this evening, the moderator couldn't even keep up with me.
I am including a link that includes finer details, though the moderator at that site has added a lot of things, too.