Jutta and others:
I have learned that my Add-in to show image dates is currently not working. It performed a hard Identify on the World Imagery service, and (I believe) the URL for the service might have changed.
While researching the issue, however, I discovered that if the World Imagery is added to ArcGIS Explorer Desktop as a layer, and not used as a basemap, that the Identify function does work! See attached snapshot.
To add the service as a layer, Add Content, Add GIS Services, New Server Connection, http://services.arcgisonline.com/ArcGIS/services, and then add the World_Imagery service. With that layer visible, click anywhere on your map.
I was quite pleased with this. I'm not sure if ESRI recently enabled this function, or I missed it in my research. Probably the latter. 🙂