It was twenty years ago today that Sgt. Pepper taught the… Oh wait. Sorry.

It was forty years ago today that the United Kingdom and Ireland went to the decimal system for currency. Before that there were 240 pennies to the pound, which just seems incredibly confusing to us, but the switch to 100 needed some explaining, as this video we nicked from The Awl attests.

Still confused? Perhaps you need to watch another PSA.

Or maybe you prefer to learn in song.

So go out there and spend some pennies, people. It’s your civic duty. Just don’t think about where they’ve been.