If you need to use DateTimePicker, you actually need to install the Extended.Wpf.Toolkit package through NuGet:

Then add the following namespace reference to your XAML file: xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit" Finally, use the DateTimePicker control in GridL, for example: <xctk:DateTimePicker Name="dateTimePicker" Format="FullDateTime" />