Original: The WiiWare service was officially launched on March 25, 2008 in Japan,GameSpot Press Release on May 12, 2008 in North America, and on May 20, 2008 in Europe and Australia (PAL Regions).
Simplified: WiiWare was first available in Japan on March 25, 2008, then in North America on May 12, 2008, and in Europe and Australia on May 19, 2008.