I know this might be kinda confusing but...
In Exodus Part 2, Jack tells Locke that he doesn't believe in destiny. Locke then answers "Yes you do, you just don't know it yet."
Then, in the last couple episodes of Season 5, 30 years before Jack and Locke's conversation, all Jack basically talks about is destiny.
Now, in Season 1 Jack doesn't believe in destiny but 30 years ago he does. So did Locke know about Jack being in the 70's and believing in destiny?