1Password is a local, encrypted store of known passwords. Nothing is generated, except for the original passphrases themselves, which are completely random (not from a seed).
Yeah, I was a little too quick in writing that. What I meant to write was that 1. passwords are stored locally and 2. you have the option to generate passwords with predefined complexity parameters. It would be possible to use this password generating feature to update your passwords automatically at a set interval.