I believe it was after the ‘reforms’ of the Second Vatican Council that the descriptor ‘Ordinary Time’ came into common parlance. The Liturgical Calendar is punctuated by so many feasts and two huge seasons, that it might appear like the ordinary is out of place. In the same way that Advent and Lent were supposed to lead us to Christ, perhaps ordinary time was as well.
When we look at the liturgical calendar, the looming rhetorical question that comes to the mind of the Christian becomes: is any time just ‘ordinary’ with our God. The Father in providence has written every page of history already, and Jesus is alive and reigning every day the same. Likewise the every time a person confesses Christ, prays, or does an action of love, it is actually God the Spirit working in them. In this world so constantly interrupted by the Holy Trinity, ANY time can easily be transformed from ordinary to extraordinary.
That deals with the negative connotations that we set with ordinary, and in this sense, Ordinary Time in the Calendar is didactic and rhetorical. It fills the space of the question mark. However, there is also a sense in which God never changes. After all, the ancient prayer is still “…sicut erat in principio et nunc, et semper, et in saecula saeculorum…” – “As it was in the beginning is now, and ever shall be, world without end.” God is the one after all in whom there is “no variation or shadow due to change” (Jms. 1:17). We can trust even in the most ordinary and seemingly God-less circumstances – in places and times we can’t see or feel God, that nonetheless He is there, as much as He was during the most eventful of times, it is not He, but us who have changed.