Knowers in time have access to the time with T, and perhaps T itself, only at that time, so what changes over time is not what is true but what temporal believers have access to.
Edward Wierenga (1989, 175–90) offered two replies to the argument, based on differing accounts of what propositions are believed and the requirements of omniscience. On the first, an omniscient being would know all truths, propositions expressed by present-tensed sentences predicate properties of whatever time has a time-haecceity T, but they and all other propositions are eternally true. Knowers in time have access to the time with T, and perhaps T itself, only at that time: so what changes over time is not what is true, but what temporal believers have access to. But (Wierenga notes) the...