Thanks for your reply Shankar. While the document indeed is very helpful its not quite what I'm looking for. As far as I understand the reporting discussed in the document you link to will happen only on the full end to end time spend on the change process.
What we aim to do, is reporting on the different approval steps that a change needs to go through before full completion. In order to control the approval process, workflows based on template WS60800086are being set up. It is these that we now want to create reporting on. For this I would very much like some standard extractors that would give me information such as for example the "arrival time" and "departure time" for a change to an approver.