GPSBabel did not create the KML you're showing us. (I recognize our KML output like handwriting...) There are no timestamps in that KML.
I demonstrated that reading the GPX you showed us generates KML that contains 27,130 timestamps from 2010.
Please be precise (I loaded file A into GPSBabel with the following options and chose output O with options X) when requesting help. You asked us to tell you what you were "doing wrong", but you've not described what you're actually doing. Include screenshots if necessary. Your goal should be fore any one of our several hundred members on this list perform the same steps and see the same thing and offer help.