User blog comment:Willbachbakal/(Champion Rework) Zilean, the Chronokeeper/@comment-3297251-20130806065336/@comment-3297251-20130806174550

I still think you should limit that to 40 CDR. At max level with 60% Zilean would be one of the most damaging mage late game with heavy (like, really heavy) sustained damage (175% AP scaling every 4 seconds ? yes please).

Either give him an active 40% CDR or a passive amount of CDR (max 20) which doubles upon activation.