It is very easy to import national holidays, school vacation dates etc. into your calendar:

Importing calendar entries:

• Log in to interWaysMAIL Webmail (https://ssl.interways.de)
• Click in Preferences (Options) --> Calendar

• Go to the "Import/Export" section
• Click on "Import file", choose the .ics file you have downloaded and continue
• Choose the calendar you want to import the data into
• Alternatively, you can import the data directly into iCal, Thunderbird, etc...!

Where do I find these calendar data files?

• Easy method: Open Webmail (https://ssl.interways.de), click on "Zimlets" on the left; click on "Holiday Calendars". Then you can choose a list of countries and import holiday dates. A corresponding calendar is created automatically. It is also synced to Outlook/iCal/DesktopApplication/iPhone, ...

• Using your preferred search engine, e.g. Google oder Yahoo!, search for: ics holidays  or similar phrases