That's really neat.
But now, I really want to know why my office suite needs to tell my printer what day of the week it is.
If the printer is smart enough to make use of that kind of information, then isn't it also smart enough to sort that out on its own? If so, then it seems superfluous.
Can be useful to distinguish when a print job was submitted from when it was actually received by the printer. That distinction matters when printers go offline and jobs get queued.
Doesn't seem to me like it is telling the printer what day of the week it is because the printer needs to know so much as it is generating a PostScript file for the printer to use and is adding the creation date as either a convention or requirement of the format, and not the printer.