It could have been possible to determine when the Messiah would come; after all, there were scriptural indicators.
Daniel prophesied, “Know therefore and understand, that from the going forth of the command to restore and build Jerusalem until Messiah the Prince, there shall be seven weeks and sixty-two weeks; Dan 9:25
It seems to tell an exact time for Messiah with the command to restore and build Jerusalem in the forefront and the arrival of Messiah in the end.
Of course there is much more to this prophecy that still deals with our future.
Another indication was from a little known prophet called Micah.
But you, Bethlehem Ephrathah, though you are little among the thousands of Judah,
Yet out of you shall come forth to Me the One to be Ruler in Israel, whose goings forth are from of old, from everlasting. Mic 5:2
This is the scripture Herod was given when he asked his scholars where Christ was to be born, yet he didn’t go to see Him.
The Bible is not a book of mystery but the revealing of God to us so that we may know and understand Him; at least as much as He wants us too.
Is it a complete biography and record of all that God has done?
No!
Even the four Gospels and the life of Jesus are condensed for us.
And there are also many other things that Jesus did, which if they were written one by one, I suppose that even the world itself could not contain the books that would be written. Amen. John 21:25
The only way to know God and His plan is to read the Bible and pray for understanding.
The one danger of this is going outside scripture to explain certain things.
Do not add to it and do not take away from it.