In Europe, there are two parallel realities which coexist, have some influence over one another, but are ultimately somewhat separate.

There's the real reality, and then there's the reality as it is perceived by the bureaucratic apparatus, the "upside down." It's important to realize that everything in the "upside down" must be consistent with the rest of that reality, but not necessarily with what actually happened in the real world. The closer your activities get to the government and government scrutiny, the more true that description is.

Did John have to go somewhere on Monday and finish his work on Saturday instead? He could have filed for time off and then gotten special permission to work on Saturday, but that's far too many forms with far too many signatures. It's just easier to pretend (on all documents, yes all of them, the "upside down" demands consistency) that he did in fact work on Monday and did not work on saturday. Americans call it fraud, Europeans call it Tuesday.