The time-dilation at the surface of a [matter] neutron star is calculated to approximately be four times slower than flat space-time, conventional quantum mechanics treats antiparticles as traveling backwards in time, but we may never observe an antineutron star because of baryon asymmetry, stable antinuclei have been produced at several facilities so stable anti-neutronium is definitely possible, the real core question about antimatter is how it affects time.
Addendum: to be clear, I'm asking for an explanation/answer that jives with conventional understanding such as: gravitons are a conventional extension of the SM, matter and antimatter are considered different kinds of mass NOT "antimass", ergo, time-dilation near an antineutron star should be exactly the same as time-dilation near a neutron star - with the explicit understanding that we consider antimatter generating gravitons exactly the same as matter, that's the kind of answer i'm looking for.
