The Broken Window Theory was introduced to software development by Andy Hunt and Dave Thomas in The Pragmatic Programmer. In the programming world, the story goes, if you accept one broken window (aka bad code) in your software project, soon everything will be smashed and fall apart. Many articles have been written about that.
And here we have yet another real-world example. The advent calendar was sent to us by a business partner and for 16 days only one window was opened per day. Whoever came into the office first and found that day still closed could enjoy a piece of chocolate. Everybody else did not.
Then one of our colleagues opened a window that should not have been opened yet. The sin was committed, the rule caught hold, and within a day the calendar was empty.