Revelation 10:7 "...but in the days of the voice of the seventh angel, when he is about to sound, then the mystery of God is finished, as He preached to His servants the prophets."
This harmony is designed for the purpose of having specific biblical prophecies coherently together so that the rich imagery and vivid details of the Scripture can be clearly seen. This will also demonstrate the unity of the Bible, particularly God's promises, covenants, law, gospel and His Messiah. Much of the imagery and vividness has been dismissed as figurative and all sorts of interpretations have been fashioned to discredit the authenticity and supernatural orgin of these prophecies.
Yet what is so important to Christians, is that when Isaiah, Zechariah, and all the other Old Testament Prophets spoke, they were not only inspired by the Holy Spirit to speak and write, but declared the same truths as Jesus, Peter, Paul and John. There is no discrepancy between them, no discrepancy of context, meaning or application. This is what this harmony is all about. I plan to continually add to it as my study of this subject grows.
Also, please consider the Messianic prophecies of the Old Testament, how they were given, and the fact that only Zechariah & Elizabeth, John The Baptist, Mary & Joseph, Simeon, Anna and the Magi were looking for His Advent. Also notice that it came through supernatural intervention for their own understanding. The family's understanding through angelic annoucement and signs, the Magi through Daniel's teachings. Even with all the descriptive prophecies given, very few were watching and waiting. It took God's angelic host to announce His Birth to the shepherds. Might we consider our watching and waiting...
Please take the time to investigate each verse in it own context. Many times, we miss the meaning by just reading one or two verses and ignoring the rest of the passage.