Wday is work in progress. That is to say, it is complete, but to make it more useful there needs to be input from others. Since it involves the culture of many countries, I can't do it all myself. Please consider contributing some time to make it a really useful bit of software.
Wday is fully internationalised. So far, there is only a German and an English localisation. If you're a native (or very good) speaker of another language, then please contribute a translation.
Finding out the rules used by your local government is usually just a matter of a few hours research at your local library or on the Internet. Most countries have several administrative regions (States, Principalities, Lander, Cantons etc) all with different holidays. It's best to find out the rules for all the regions in your country and do them all at once.
By default, Wday uses the current region. It determines this by a number of different algorithms (primarily to examine the system's timezone). This is known to work on Debian GNU/Linux and Solaris. Unfortunately, different operating systems have different methods to determine these settings. If you have the resources, please try wday on another platform.
Bug Reports? In the unlikely event of it not working properly, please report this.