Regarding the xml.utils.iso8601: I will definitely abandon that module, since it's very problematic under certain circumstances.

I will use the dateutil module (additional dependency, but that package is available in Extra).

This means that I have to publish another version before the one with the GUI, since as you can imagine date handling is quite critical in Erminig, so I want to be sure that there is no hidden surprise somewhere with that new module.

Concerning the GUI: I will post a few screenshots of the mock-ups in the next few days.