I once missed the deadline for an essay. It was due in by 4pm on a Friday, I thought it was due in for the following Wednesday, realised my mistake around 5.30pm Friday. Ooops. We drop down a grade point (i.e. from A1 to A2 or B3 to C1) for every day late it is. So I finished it by midday on Saturday, uploaded the electronic copy and went to hand in the paper copy to the office. Not just the office but the entire building was locked up. No way to hand it in. So I emailed a PDF to the markers and CC'd the course organisers explaining my mistake. I also handed in a paper copy before 9am on Monday.
I was then informed that because I couldn't hand in a physical copy for Monday, it was going to be counted as 3 days late rather than one. Which meant it would be physically impossible to get anything higher than a B1 for that project. I contested. I was happy (for a given definition of happy) to lose one grade point. After all it was me that made the mistake. But to lose 3 automatically just because it was over the weekend? Not cool.
Ultimately, I think I got no deductions, but due to the exceptional circumstances form I had handed in for everything else going on rather than because I had successfully fought their stupid system.