I remember that there was a lot of sibling rivalry involved. Not all of ours had chocolate, though - sometimes there were just little pictures or verses. My German cousins always had a cooler calendar than ours.
My German friends have reusable ones. They're made up of little cloth pouches and their mother buys those individually wrapped Darrell Lea chocolates to fill them with. I don't think she leaves a chocolate for everday, either, come to think of it. There's probably some true-meaning-of-Christmas stuff in there too.
Personally I like to wait until after Christmas and buy five for a dollar at the supermarket and eat them all at once :D
Oh my. The advent calendars appeared in our local stores in October. I was very shocked because the Christmas stuff comes to the shops earlier and earlier every year. Or maybe I just haven't noticed before.
Oh, and the point was that they are common in Finland, too. The children like chocolate calendars but then there are those ones which have pictures in them. The advent calendar of The Guides and Scouts of Finland is very famous here and it's always very interesting and has a high quality.
Well, I found this link. There are pictures of all of the scout calendars before the doors are opened. Unfortunately the text is in Finnish, but when you click the blue links, you can search the different decades.