This is not merely just a calendar, but can be viewed more like a "pivot table". The dimensions are Teams (Groups are just groups of Teams), Cities, and Time. Pick one, and it shows you the intersections with the other two (well, shows matches and places the teams in the matches). Very clever UI design for a traditional "Business Intelligence" report in the Enterprise world. Perhaps something like this is applicable to http://ycombinator.com/rfs2.html. The trick is that this "calendar" has limited amount of items in each dimension.