I was trying to figure out the 'story world' timespan of the four episodes...is it four straight days, or a week, or something?
The first episode seems to be all on the same day; the second, also one; the third appears to be the longest, but it could be just the confusion of them running around to so many different places; and the fourth is one day, from beginning to end.
Note that by the follow-up episode, they still have to go to work. I don't think they work on Saturdays, so it would fit in with that episode being on a Friday. This would make the four parts of the arc Monday through Thursday.
I think you're right, queensgirl. I believe that each episode spanned one day. Beginning with Sam and Dave, there are references to the events of the day or night before which seem to follow that timeline.