WPF 4.0 has no default DateTime control, (only DatePicker) which means we need to add it on our own.
I found a very cozy way to do it.
1. Navigate here, download the provided dll and add it to the project (add reference of course).
2. Add to the Window XAML: xmlns:wpfx="http://schemas.microsoft.com/winfx/2006/xaml/presentation/toolkit/extended"
3. Add <wpfx:DateTimePicker/> where you want your DateTime control to be, modify it with desired preferences.