non-ordinary Ordinary Time. . .

If you are Roman Catholic, you have been observing these Sundays since Christmas ended as Sundays in Ordinary Time.  You noted the change when the color shifted from white to green.  It is all the doing of the liturgical and lectionary changes that followed Vatican II.  Prior to that time (1970), the Sundays were announced according to their season (Sundays after Epiphany or Trinity).  Now they have to live with the rather dull sounding name Ordinary Time.  But this word does not mean the typical definition of "ordinary" but ordinary in the sense of ordinal.  They are counted as the weeks of the year.  So when Epiphany no longer counted the Sundays, they became the first Sunday in Ordinary Time (quite literally the first Sunday of the time counted through the year as opposed to after a feast).

Lutherans, at least the LCMS kind, did not take to this.  Ordinary was, well, just too ordinary and we kept the nomenclature of after Epiphany for these Sundays now coming to an end or after Pentecost for those in the other green season, the longer one.  Those in the one year lectionary call them Sundays after Trinity.  We keep the tie to the feast so that the feast continues to set the tone for the whole of the season (up to 8 Sundays after Epiphany and too many to remember after Pentecost).

Since Easter does not cooperate with our penchant for order and varies from early to late and late to early, it messes up our nice and orderly way of counting time.  But Easter is not only to blame.  Sometimes (2016 was one) we ended up with no real Sundays after Christmas (the Circumcision and Name of Jesus was Sunday, January 1, and then we skipped right over January 6 to the Baptism of our Lord, the first Sunday after Epiphany).  Christmas (and Easter) tend to foul up our desire to keep things counting progressively and the lectionary can literally have us move from birth to age 12 to age 2 or so and the appearance of the Magi and it can leave us with Sundays to spare in a season shortened because Easter is early this year and something has got to give.

Rome ended up with the problem of what to do with those Sundays left unused after Epiphany (at least in the Pre-Vatican II calendar) and they solved it by adding them onto the end of the year.  At the end of the liturgical year, an oddity happens in the traditional calendar. Left over Sundays reappear and added back in until the liturgical year is concluded.  This is, of course, due the moon and shifting date of Easter, and therefore Ash Wednesday and Pentecost.  Depending on when they fall, the Sundays after Pentecost might not take you all the way to Advent.  So, Sundays never used prior to Ash Wednesday suddenly appear and get added back in (at least for those using the Extraordianary Form which is, by the way, not at all ordinary).

There are all sorts of things we do to order the calendar, especially in ordinary time.  For Lutherans this means skipping some Sundays at the very beginning of the Pentecost season.  Unfortunately, we never add them back in.  We solve the dilemma by adding enough pericopes to have more than enough no matter the whims of the moon, Easter, Ash Wednesday, and Pentecost (the most movable of feasts).   So much for the rubrics (the red letter rules that tell us what day it is and what pericopes belong to it).  Just thought you would like to know. . .