Steve,Correct, time-awareness is added by the feature layer and isn't supported on the graphics layer. As you mentioned you can create a feature collection that is time-aware and use that with the time slider. Here's a sample that creates a time-aware feature layer based on a feature collection:http://help.arcgis.com/en/webapi/javascript/arcgis/help/jssamples/mobile_geolocaterenderer.html