A typical headrest of a taxi in Shenzhen:

Can you guess what it says?  You might be surprised to find out that the text simply means “Monday”.  This method guarantees that the headrest cover has been replaced the same day (or exactly a week before…). Of course, nothing prevents the driver from simply putting back on the same dirty cover that he took off last week (without washing it), but at least there are seven dirty covers instead of just one… lets them get a whiff of fresh air on their week off!