Thanks, VVFanatic.

This also explains why "time travel" by changing the time on your computer is so risky. Everything for VV2 (and VV1, as well, I bet) is based on the computer's clock. That's why it runs even when you're not playing it. If a person changes their computer clock, the entire game is changed with it. So when that person changes their computer clock again, backwards, it throws everything into a mess. How do you subtract time?
It's clear that it's all based on a mathematical equation, using the computer's clock as an integral part of that equation. Changing the clock forward makes that equation spit out very high numbers, radically changing the game (a villager 70 years old may suddenly "age" to 100; therefore, dying, while there were no new babies during that "time").
But the real problem is when the computer clock is moved backwards. Then the equation spits out negative numbers. How can a child 5 years old suddenly be -3 years old? Not possible. You can't undo a birth. I have no idea what happens under those circumstances (I don't play with my computer clock), but the end result would surely be undesirable in the long run.
It all makes sense to me now.
