Y2K was a big deal. Massive code reviews/rewrites along with incorporating the new technologies of the day prevented what could have happened if nothing had been done. It wasn't just "a bug", but rather "all the small bugs all over the fucking place". Some of the effort went towards areas not directly/technically Y2K related. It lead to a dimple in the economy as the budgets for Y2K projects disappeared and weren't replaced. But, in the end, instead of the date bug, we got the hanging chad bug.