In Hebrew, the word for Passover, Pesach (פסח), reads Peh Sach (פה סח), "a talking mouth." Pesach celebrates freedom, first and foremost – freedom of speech.
God does not reveal, even to the greatest of prophets, exactly when the Mashiach will come and bring redemption to the world. God wants us to believe that Mashiach can arrive this very day, and pray as earnestly as we can that he indeed arrives today. The sages have provided us with various signs to know when the time is ripe, but we can never really know for sure, we can only believe and pray. This is exactly what God wants, for He desires that we nurture in our souls messianic consciousness, a state of consciousness that is not one of knowledge but one of faith and prayer.
"His heart does not (and cannot) inform His mouth." This is the idiom the sages use to describe the block that exists, as it were, between God's heart and mouth, i.e., His inability to reveal to us the date of redemption.
We all can identify with God in this respect. We all know how difficult and virtually impossible it is to express in words our deepest thoughts and feelings, those that lie hidden away in our hearts.
The ability to delve into the depths of our hearts and find the correct words to give verbal expression to our hitherto unconscious thoughts and feelings is itself the secret of the coming of our individual, personal Mashiach.
Similarly, for God to tell us when Mashiach will come is itself the coming of Mashiach. To tell us that Mashiach will come tomorrow is not to tell us at all! Mashiach is the revelation of God's heart to us, so when He tells of his arrival he is already here.
Pesach is the holiday of freedom – freedom of speech. Not just freedom to express in words our conscious thoughts, but freedom to express the depths of our unconscious, the depths of our faith (we eat matzah, "the food of faith," in order to speak words of faith). God begins to express Himself to us by liberating us from Egypt on the external, physical plane, thereby arousing us to give expression to ourselves. Our self-expression then arouses Him to give absolute expression to Himself. This is the coming of the Mashiach.