Do you have time? Or, do you have the time?

What is the difference between the two expressions in the title above?  For an example of what can happen when you confuse these two expressions, please read this post at my sister blog.  I have used the example in listening and vocabulary classes in addition to dedicated grammar classes. When students think that articles are not significant, it might help them to pay more attention if they have a clear image of how one little word like "the" created an embarrassing misunderstanding.