What should "value_from_datadict" method of a custom form widget return?
The Django source says 

Given a 
  dictionary of data and this widget's
  name, returns the value of this
  widget. Returns None if it's not
  provided.

Reading the code, I see that Django's separate Date and Time widgets are both subclasses of Input, subclasses of Widget, which appears to work with simple Strings.
I'm trying to build my own custom django form widgets (putting them in widgets.py of my project directory).  What should the value "value_from_datadict()" return?  Is it returning a string or the actual expected value of the field?
I'm building my own version of a split date/time widget using JQuery objects, what should each part of the widget return?  Should the date widget return a datetime and the time widget return a datetime?  What glue code merges the two values together?