I’m just curious how this works in practice.

When you say something like “Let’s meet up this weekend”, is it implied that you will meet on Saturday, since Sunday is the other end of next week, so technically a different weekend?

A string is reversible, a week is not. A week has a beginning and an end.

Is this a thing outside the USA? It always bugs me when apps default to this. How does it make any sense for the week to start with the weekend?