I am altering a view using hook_views_data_alter to display a date range filter.
I was able to create the form to look the way I wanted with hook_form_alter.
It looks like this:
Start Date: (textfield, the value of which is a filter)
End Date: (textfield, the value of which is a filter)
Now, this works and it filters successfully. What I'm having a hard time with, though, is a pair of radio buttons I'm generating in hook_form_alter.