What I heard was the organizers cut his time slot first, to accomodate Usher. Then later reduced it further and prompted him to end the act in one minute. If that's the case, he is more than justified. The band PR later issued statement saying they were the wrong ones and the organizers never cut their allocated slot. It could be that they caved in, or it could be they were in the wrong from beginning.

Whatever the case be, I let them sort it out. Green Day was, and will remain, one of the better punk rocks that came out of the 90 (late 80s).