Yeah it was sort of a gradual evolution, hard trance started to get harder and the gabba influences slowly came in. Q-Dance in Holland were (I beleive) the first to actually name it hardstyle, and it grew from there. They've always had different genre labels to us though, i'm surprised that it took off here - I went a few years back, at the height of the Scot Project era to Amsterdam, and all the hard trance was labeled hard house there. I guess they never had hard house there (lucky bastards).

Of course now that hardstyle has become quite tightly defined in it's own right, you can look back and pick out records that you might have called hardstyle if the defintion had been around then, but i'd personally say that that hardstyle as a defined genre has been around for about 2 years.