Where is DatePicker in the packages?

Just wondering where the https://github.com/dotnetprojects/WpfToolkit/blob/725683d918aa4f5c9d819259dd69bcbdcd5203db/WpfToolkit/DatePicker/Microsoft/Windows/Controls/DatePicker.cs

Is bundled in? I can't seem to see it, is the premise that it's inside the framework so it's excluded? 

We are depending on these nuget packages for a multi-targetted backwards compatibility suppport.

