When was Sergeant Pepper's Lonely Hearts Club Band released?

As of 2010, it is estimated that 32 million copies of Sgt Pepper's have been sold, not including what has been sold on iTunes. While this number is huge, there are many other albums that have sold more copies including Michael Jackson's "Thriller" and AC/DC's "Back in Black", which are number one and two, respectively, on the all-time best seller list.