12:01 AM PDT on Friday, April 19, 2013 and ends at 11:59 PM PDT on Sunday, April 21, 2013
more info can be found here
https://www.guildwars2.com/en/news/try-guild-wars-2-for-free-this-weekend-april-19-21/
I suggest you pre-download ahead of time as it is a pretty big game.
Keep trying took me a bunch of tries to finally get it, also a heads up it will save you time to join their steam group ahead of time, if not it will ask you to instead of getting the code and you have to retry again.
Thanks OP snagged last one with DLC + they had legend of zelda for 19.99 + soundtrack though they did have to call a manager because it rung 49.99 but the sticker said 19.99 not sure if mistake or if every kmart has this.