Clock for the chronically late

This clock is perfect for people like me who have trouble being on time for things. It's not that I don't care about the people I'm seeing, it's that everything takes longer than I expect it to, so I'm late. Setting my clock 15 minutes fast, or whatever, has never worked, since I *know* it's fast, so I have more time. This often leads to me being later, since I don't trust my clock.

The unpredictability of this clock is a genius idea, you have no choice but to work to it, since you don't know how fast it is, if at all. I await the physical version eagerly.