In the liturgical year, there are two periods of time that are referred to as “ordinary” or “common” time. One begins after Christmastide and ends on the day before Ash Wednesday (“Fat Tuesday”), while the other starts the day after Pentecost and ends the day before Christ the King Sunday. A graphic may help make it clear:
At one time, the weeks in these periods were numbered, as “the 1st Sunday after Pentecost” and “the 2nd Sunday after Pentecost.” The term ordinary, then, is not used to mean these are not-special times <g>, but that these weeks were called by “ordinals” or numbers.
The last Sunday in the liturgical year is Christ the King Sunday, where we celebrate the return and reign of Christ. The next Sunday is the first Sunday of Advent, and we start the year anew.