question: why is the “holiday script” not a discrete plugin instead of three loose scripts??
The number of developers on pimatic is still relatively small and it is leisure time work for everybody. If you think this should be a plugin you can make feature request and contribute to it (requirements and conceptual ideas at least, if you don’t have software development skills).
As @leader21 mentioned the google calendard plugin this may be one approach to it. I am sure there are tools for importing to holiday schedules to google calendar (for example using ical-files http://de-kalender.de/icalendar).
Regarding the existing bash scripts I think this is a nice solution, but it is fragile - if the site structure changes the scripts are likely to break and need to be adapted. So, it would be better to use a REST web service for holidays.