Waypoint script - jscript variable declaration error

A customer complained we are not declaring expires before using it in the pixel
script at http://thesearchagency.net/tsawaypoint.php

expires = new Date( today.getTime() + (86400000 * 1000) );

I believe not declaring it makes it available outside the javascript function?
Looking at the code, it does not apper to need to be available and I suppose
there is a chance our use of expires may collide with another piece of code with
the same error.

That said, I am not too worried ....