Date CCK fields are not available as an argument/filter in a view.

I've created a content type called "event" with a date field call starttime. I created a few "event"s, then chose to create a view. In the view, I am unable to choose the starttime field as an argument or filter. What's odd is I can select it in the "fields" and "sort criteria" components of the views interface. Am I doing something wrong or is this a bug?