John 13:18  I speak not of you all: I know whom I have chosen: but that the scripture may be fulfilled, He that eateth bread with me hath lifted up his heel against me.
19  Now I tell you before it come, that, when it is come to pass, ye may believe that I am he.

John 14:28  Ye have heard how I said unto you, I go away, and come again unto you. If ye loved me, ye would rejoice, because I said, I go unto the Father: for my Father is greater than I.
29  And now I have told you before it come to pass, that, when it is come to pass, ye might believe.
God reveals the future so that we might believe.
When we see the prophecied signs of the times coming to pass, we should remember that He told us before it came to pass (two millennia before, in fact), so that we might believe His words, and lift up our heads with joy, because His coming is so much nearer.