Although "end", when used for time, usually refers to the chronologically later boundary of a period, there are other senses of the word in which an end can als

Although "end", when used for time, usually refers to the chronologically later boundary of a period, there are other senses of the word in which an end can also be a start: a line has two ends, and we say "from end to end", for example. Thus, I don't think it's necessarily contradictory to speak of an end of a week that also comes at the start - and that's without even thinking about the inherently cyclical nature of the week.