Baltimore's 9/11 Memorial as a sundial

I was a scientific consultant for the 9/11 memorial being constructed in Baltimore's Inner Harbor by a local architectural firm. They wanted the memorial to work like a sundial with the adjacent World Trade Center (WTC) building (pictured above). I really just verified their calculations of how the shadow of the WTC would sweep across the plaza, which had to be predicted several months in advance. They put small notches in the base of the memorial denoting the horrible timeline of events on the morning of 11 September 2001, and only on September 11 of each year the shadow would align with each of the notches at the corresponding time. The memorial was unveiled on the 10th anniversary of 9/11. Alas, it was a cloudy day so we could not verify the accuracy of the sundial, but the architect reassured me that the shadows were perfectly offset just a few days before September 11.