If memory serves, it was 1948--that's where the 84 came from. 1969 is, of course, "zero" in Unix years, and the default if the computer "forgets" what time it is.
And this isn't necessarily normal, but since you have a PowerBook (I guess you didn't have a problem installing it yourself), I believe it's totally normal if you took the battery out like you're supposed to. As said, so long as nothing else is acting up, just reset it and forget about it.
[edit: realized you did have a PB from your other thread]