I'm not sure if this project is still active, but would it be possible to request a couple of new features in vzic:
1. Option to produce a METHOD:PUBLISH property in generated iCalendar objects. This should probably be controlled by a flag to allow for enabling/disabling as required.
2. Addition of a LAST-MODIFIED property on all VTIMEZONE objects. The value should correspond to a timestamp of the execution.
I would be happy to investigate adding this support myself, however I'm not sure what the status of the project is right now..
I have also noticed that vzic doesn't seem to parse the latest versions of Olson DB entirely, with a few definitions missing from the results (I think America/Argentina is one example). Any info you can offer on this would be greatly appreciated.