I don't know how it is in other countries but every year at the end of February there's a huge clearance sale in every book store all over Sweden. It all started at the end of the 1920's when the publishers wanted to get rid of old books in the spring. Back then it was only books that was 5 years or older that was on the clearance sale.
It wasn't until the 1930's that the publishers agreed on a special date to start the clearance sale: mid February. Today all places who sell books come together and start the sale at a specific date, it changes each year but it's usually toward the end of February. You can of course pre-order online which has been a huge argument between the online and offline stores. The clearance sale started on the 26th of February this year and on the 22nd last year.
The national book clearance sale is even a big contender to Christmas shopping in Sweden, it has even been bigger than Christmas shopping before.
The local book store in my home town used to start the sale at midnight of the clearance sale day. There were a long line of people standing in the February cold waiting to get in. Usually it was on a school night for me so I used to go through the catalogue that was sent out and write down which books my mum had to get for me. In the morning they stood in bags in the kitchen. I remember it was like Christmas - but better as the book worm I was/am.
Is there a national book clearance sale in your country?
Sources (Swedish): wikipedia | SVF
Source (English): Sveriges radio