John Calvin: The Church has been as long as time

…we must understand, that at no period since the world began has the Lord been without his Church, nor ever shall be till the final consummation of all things. For although, at the very outset, the whole human race was vitiated and corrupted by the sin of Adam, yet of this kind of polluted mass he always sanctifies some vessels to honor, that no age may be left without experience of his mercy.

Institutes, 4.1.17