How do I get a string representation from a type?

Say I have something like

var T = Type.GetType("System.Nullable`1[[System.DateTime, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]");

which is a nullable datetime.

T.FullName gives me:

"System.Nullable`1[[System.DateTime, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]"

How can I extract DateTime? or Nullable<DateTime> as a string representation from the Type?