Once the grand finale of the Easter season, namely Pentecost, has passed us by this weekend, one might tend to think that things go "back to normal" in the liturgy. After all, we do call it "Ordinary Time", right?
But no, not exactly. For one thing, the term "ordinary" in "Ordinary Time" does not quite correspond to the,um ordinary definition: routine, normal, business-as-usual. It mostly refers to the fact that the Sundays and weeks are numbered, or "ordered". (Although we certainly can feel the contrast between the solemn events of the previous holy seasons as compared to ordinary time, so we're not entirely wrong to feel that Ordinary time is somewhat ordinary in the popular English sense of the word.)
For another thing, for those who use mostly hard copy breviaries, rather than rely on breviary websites to do their work for them, the next week or so can be among the most confusing of the entire year. Although we enter Ordinary time as of Monday, there are no Sundays of Ordinary Time until the second week of June! All this makes for plenty of head scratching as we flip here and there trying to figure things out.
So just keep an eye on your parish calendar if you forget what week we're in. Or print this post and keep it in your book.
Monday starts the 7th week of ordinary time, using week III of the Psalter. There is no 7th Sunday in ordinary time because of Pentecost.
Next Sunday is Trinity Sunday. (with its own special liturgy in the proper of Seasons. DON'T use the 8th Sunday. Continue with the 8th week (Psalter week IV) on Monday.
The Sunday after (6/02) that is Corpus Christi (with its own special liturgy), so DON"T use the 9th Sunday of Ordinary time. Continue on Monday with the 9th week and week I of the Psalter.
The next Sunday, June 9th, we finally get a Sunday of Ordinary Time, the 10th. Now you are fully back in Ordinary Time, even on Sundays. (Psalter week II)
Then we shall be back to nothing but Sundays in Ordinary time clear through until Christ the King in November.
Hope this is helpful.