The first expansion of Starcraft II is on its way to store shelves on March 12th, 2013. Just like Diablo III and the original Starcraft II, Heart of the Swarm requires you to be connected to the Battle.net server to play.
Here is the short list of time zones, and their server launch time:
Brazil Standard Time (Sao Paulo)
4:01 a.m. March 12
Eastern Daylight Saving Time
3:01 a.m. March 12
Central Daylight Saving Time
2:01 a.m. March 12
Mountain Daylight Saving Time
1:01 a.m. March 12
Pacific Daylight Saving Time
12:01 a.m. March 12
Hawaii Standard Time
9:01 p.m. March 11
These server times are still subject to change.
Blizzard is also hosting a pre-launch party, partnering with Gamestop and Twitch.tv which will begin the evening before the game releases at the Irvine Spectrum Center.
Starcraft II: Heart of the Swarm expansion is for PC and Mac, and needs Starcraft II: Wings of Liberty installed, internet, and a constant connection to Battle.net in order to play. The expansion follows up where the original Starcraft II left off, featuring the Zerg campaign.