I confess I hadn't thought that far ahead. I would be content just having the ordinal day be labeled on the x-axis so it would read something like 1,2,3....20, each representing a day.
I would also be content with just one set of dates on the x-axis mostly likely those from Group A.
I guess the holy grail would be to get both the dates on the x-axis but I think that would be rather crowded and hard to read so I'm not terribly hung up on that. The chart is rather large though so it might work.
Another interesting visual might be to have the Group A dates at the top of the graph and Group B on the bottom but I don't think that's possible in QlikView (or any other BI software I'm aware of.)