User blog comment:Sim533/Game Update September 9/@comment-2233791-20140910082017/@comment-2233791-20140911091004

The old memberships you have active do not go toward the new deal. In order to take advantage of the new offer, a new membership would need to be made. If you want the 6 month reward, you would need to purchase a 6 month membership, and same for the 12.

If you extend, then the added time would be added onto the end of your current membership. So if your membership ended on January 1st of 2015 and you purchased a 12 month membership now, then your membership would not end until January 1st of 2016.