Set the created variable in a set_once on the user service. This will make it work for github logins as well.

static/js/app.js

@@ -23,6 +23,9 @@ quayApp = angular.module('quay', ['restangular', 'angularMoment', 'angulartics',
               '$username': userResponse.username,
               'verified': userResponse.verified
             });
+            mixpanel.people.set_once({
+              '$created': new Date()
+            })
           }
         });
       };