Does Blender use Automatic Tweening/Animation? I'm entering into a competition and one of the rules states No Automatic Animation Software.

I just started using Blender and plan to use it more. 

Now, I don't know if I have lost several days worth of work, or if I merely need to unmark a checkbox.
The animation features of Blender relies heavily on keyframes and different kinds of interpolation between those. So yes, Blender does indeed use "Automatic Tweening" (but not always as cegaton mentions in the comments).

At least if "tweening" is defined as in this Wikipedia article.