Due to the absence of a built-in DatePicker control many are using the Silverlight Toolkit which has a Silverlight implementation to match the control used in the native applications. One limitation in the current release is that the UI is only available in English. The day/month names are retrieved based on the device locale but the page header and text labels for buttons are always in English. I had a look at the code to implement a fix, interestingly I found that the strings were already stored in resource files, it’s just that there were no resources for other languages. I’ve submitted a set of .resx files to cover all the currently supported Windows Phone 7 languages so hopefully my patch will be integrated in a future release. I’ve also discovered that by creating my own localised resource dlls from the latest source I can use them against the current release binary. We are sharing these files for other developers who use these controls and write multi-language software for Windows Phone. To use these simply copy the contents of the ZIP file into the install folder for the November 2010 toolkit on your machine which will be somewhere similar to “C:Program Files (x86)Microsoft SDKsWindows Phonev7.0ToolkitNov10Bin”. As a bonus these resources also localise the On/Off text on the ToggleButton control.
If you’ve not attempted building a localised application before have a look at this article on MSDN – http://msdn.microsoft.com/en-us/library/ff637520(v=VS.92).aspx. Mostly this involves standard RESX editing but for Windows Phone you have to make a minor edit to your project file with a text editor, hopefully this can be fixed in a Visual Studio Patch/Service Pack.