God's true prophets have been persecuted from the beginning. Abel, son of Adam and Eve, was the first, according to Jesus, for his blood was shed by Cain "from the foundation of the world." A "prophet" in biblical terms was a man who proclaimed inspired words from God (not necessarily predictions of the future, but words inspired by the Holy Spirit--note 1 Peter 1:10-11; 2 Peter 1:19-21).
Evidently Abel was speaking God's own words to Cain when the latter slew him in jealous wrath. The Zacharias mentioned is probably "Zechariah the son of Jehoiada the priest," who was stoned when he prophesied against the people under King Joash (2 Chronicles 24:20-22), for he was the last prophet actually mentioned in the Old Testament as having been slain for his testimony.
Thus the period encompassed by the Lord's statement was the entire Old Testament period, "from the foundation of the world" to the coming of Christ. The same experience awaited most of the prophets used by God to pen the New Testament Scriptures. Thus does the world react to God's inspired Word!
There is another important truth in this passage. The blood of God's prophets began to be shed "from the foundation of the world," not just beginning almost five billion years after the foundation of the world, as modern evolutionists allege! This is striking confirmation that the world was made from start to finish in six literal days. See also Mark 10:6, Acts 3:21, etc., for similar incidental confirmations of this truth. HMM http://www.icr.org/articles/type/6/