I sent in my application in late October of last year, and they called me in mid-January to offer an interview in late February.
The time it takes can vary, because they interview in various locations around the world. If you live in North America, for instance, they may choose to interview you but they'll wait untill they have a chance to schedule more interveiws in North America. They may have to wrap up a few months of interviewing in Europe and Australia and so forth, before scheduling the interviews in the USA or Canada again.
So, you just have to wait untill they come around to your part of the world again.