Client Clock

I was looking at my system clock and the clock in the SL client and knowticed that my clock was 2 minutes behind. So, I figured, "Lets change that, so that they are the same (sans time zone difference)" and bumped my clock forward about a minute and a half.
Odd, I'm still 2 minutes behind.
Another 2 minute push.
Still 2 minutes behind.

WTF?!?

Push the HOUR hand on my clock forward, the SL client did the same.

So, I pose this question:

Why is the client clock based on my system time +2 minutes +<number of hours for timezone difference> and not just +<number of hours for timezone difference>? Why the 2 minutes? Why is it based on my clock at all?