I (and my interlocutors) have often experienced confusion when communicating with others regarding "last [day-of-week]", "this [day-of-week]" and "next [day-of-week]"
In my mind, what is logical is that "last" means the last one (the one in the most recent past); "this" means the next one coming up; and "next" is the second one from now.
"This" to me denotes the future - it points forward in time.
For example, today is Tuesday, April 14th. If I say, "last Saturday" I mean April 11th; if I say, "this Saturday" I mean April 18th; and if I say "next Saturday" I mean April 25th - although I admit it gets a little ambiguous when "this" saturday is several days away. But I would definitely be speaking of the 22nd if I were to say, "next Wednesday" (not the 15th, for that is tomorrow, and to say "next" would sound/seem bizarre to me.
Note/Addendum: I would not say "last Monday" for yesterday, because in that case I simply say that ("yesterday"); similary, I would not call tomorrow "this Wednesday" for a similar reason - I refer to that simply as "tomorrow".
I find, though, that many people consider "this Monday" to have been yesterday (the 13th), not "this coming" Monday (which is how I see it).
I do recognize some logic in this alternate viewpoint provided everybody were to agree that the "this" refers to a current week, beginning on Sunday, or Monday, depending on which day is considered a week's beginning point (and so, the differing standard in regards to that question is a matter of contention/confusion in and of itself).
Another way of expressing it, I guess, would be to say that I always consider myself as being in a sliding scale of time, rather than in a particular calendar week, one which stays fixed for an entire week. In other words, today I am in a week that runs from Tuesday the 14th through Monday the 20th. Tomorrow I will be in a week that runs from Wednesday the 15th through Tuesday 21st, etc. Others apparently always view themselves as being somewhere in a week that runs either from Sunday-Saturday, or Monday-Sunday.
Am I definitely wrong in my take on "last, this, and next" or is it just "different strokes for different folks"? I'm curious how many others (if any?) view time from "my" perspective?
The bottom line is, I always find it beneficial to mention specific dates. So, instead of saying just "this Monday" I say, "this Monday, the 20th"