necro weed posting considered harmful

on the other hand /prog/ actually was good once

Hey /prog/, I tried whipping up a quick greasemonkey script to hide the necrothreads, but I can't see why this doesn't remove all threads not created this year. Any chance you can tell me where I've went wrong?
var dateregex = /^2010/;
var threads = document.getElementsByClassName('thread');
for (i=0; i<threads.length; i++) {
  var thread = threads[i];
  var opdate =  thread.getElementsByClassName('posterdate')[0].firstChild.nodeValue;
  if (!dateregex.test(opdate)) {
    var parent = thread.parentNode;
    var grandparent = parent.parentNode;
    grandparent.removeChild(parent);
  }
}