WARNING: Minor Glee spoilers ahead. If you haven't seen this week's episode yet, you may want to come back tomorrow.
We missed last week's Glee recap because of the holiday, so it's time to pack two episodes into one post. This will work out well, because we absolutely must assume most of these episodes take place in parallel, as we're about to see.
Last week, we met the competition for Sectionals. We don't really know when Will met with their respective choirmasters, but we do know that the rehearsal with the School for the Deaf took place on Monday. That's not the same Monday as the previous episode, so it has to be the next Monday, December 14.
This week, we find out that Sectionals are "a week from Saturday." If it's already after the Monday from last week, that means Sectionals are on St. Stephen's Day, which doesn't seem likely. Therefore, this has to have happened the previous week. That's all very well and good, but the episode still has to end later than last week's episode, because Will is no longer the Glee Club director. It is, at the earliest, December 16 - the "Imagine" rehearsal is Monday, Will sleeps in the office on Tuesday (we need the day on Tuesday to resolve other subplots), Mattressgate hits on Wednesday. Sectionals are now set in stone as December 19, there is no further way around it.
And that's what you missed on Glee. Next week we finally see Sectionals, and figure out how Emma is there and at her wedding at the same time, and perhaps resolve once and for all the fake baby plotline.