Before revision: This paper extends results from Mortimer and Williams (1991) about changes of probability measure up to random times. Many new classes of examples involving honest times and pseudo-stopping times are provided .
After revision: This paper extends results from Mortimer and Williams (1991) about changes of probability measure up to a random time under the assumptions that all martingales are continuous and that the random time avoids stopping times. We consider locally absolutely continuous measure changes up to a random time, changes of probability measure up to and after an honest time, and changes of probability measure up to a pseudo-stopping times are provided .