observance of christmas

So… there I am with 12 packages set to mail off to various parts of the world today, and I venture over to the local post office.  Of course, when I get there the place is closed.  Why, you may ask.  According to the little sign, it says they are closed for the observance of christmas.  Now, I hate to belabor the obvious, but wasn’t christmas yesterday…and, if it was how could one be so unobservant as to miss it completely, and then have to take today off.