Let's face it, it never works! You always end up standing there for a full minute, screwing up your forehead while you do the math to figure out what time it really is, debating whether this clock is 5, 10, 0r 20 minutes ahead and how late you'll be if you stay put for a few more minutes.
This is why the idea never works. You always know the clock is incorrect, so you don't get "a move on"(as my mom would say) like you should.
You're not fooling anyone with your faux punctuality! Get used to being late!