 <p>Follow this guide: <a href="http://weblogs.asp.net/psheriff/archive/2009/12/01/load-resource-dictionaries-at-runtime-in-wpf.aspx" rel="nofollow">http://weblogs.asp.net/psheriff/archive/2009/12/01/load-resource-dictionaries-at-runtime-in-wpf.aspx</a></p> <ol> <li>Create various xaml resource files, but make sure the file does not compile and copies into the bin directory instead.</li> <li>Decorate your xaml controls with <code>DynamicResource</code>s.</li> <li>Load in your resources through code.</li> </ol> <p>Basically, you are looking to "skin" your application. The code that loads in your resource file can take advantage of the <code>TimeOfDay</code> enumeration.</p> <p>If you want it automated you can even have some static class that has a timer to automatically attempt to change the resource and set the timer on the application startup. :)</p>