We have had a number of "universal time" questions on this site — basically the various OPs have been looking for a way to establish a single time reference for the galaxy. I believe that's impractical, possibly not even useful, especially since it should be possible to calculate the time on planet B for an event that occurred on planet A. A solution for one planetary pair would be the stepping stone for a solution between any two planetary pairs — and thereafter the foundation for the programmatic concept (not the SI concept) of a "universal time."
Here on planet Earth, the Great Sovereign Emperor of the Known Universe, Malodorous a la Flatuleum de la Kineticist, was assassinated by Quaternary Admiral of the Galactic Fleet, Alistair "Big Dog" Alcott. "Big Dog" wants the empire to know about the change in fiefdom as quickly as possible.
Now, the Fleet has access to
FTL, wormholes, bent space, super-Einsteinian physics, Clarkean magic, really fast ships... but let's ignore that for the purpose of this question. Information simply cannot travel faster than the speed of light.
But, whatever voodoo magic is used to transmit the information, it's receivable by every planet. How this happens is irrelevant.
For the purpose of this question, the receiving planet happens to be a thoroughly terraformed Kepler-1047(c), known to its residents as Plerte (but was probably named "Planeta de la Muerte" by its original colonists...). Orbital period: 3.2 Earth days (and if that's not movin' the mail, nothing is), so that's "one year" on Plerte. We don't know it's rotational period, but let's claim for the sake of a lot of fun that it's 40 Earth hours and it's spinning backward during it's orbit compared to the spin of Earth in its orbit. Oh, and Kepler-1047 is 2,665.4 light years from Sol.
To help everybody out, your answer can use decimal time.
The message is sent at 2:27PM (GMT+12), September 19, 2020. In decimal time, that's 0.718965325567 of the Year of Our Glorious Emperor "Big Dog," 2020 (for convenience, let's say 2020.718965325567). You, the receiver on Plerte now know where it came from (Earth) and when it was sent — Earth time.
One last thing: the converted time must be accurate to the "minute" (in decimal time, of course). So, 12 decimal points of accuracy.
Question: Assuming I've given you enough information... What equation would permit the local government on Plerte to convert the event date and time to Plerte local time?
It's worth noting that at 2,665.4 light years it should be true that the two planets have changed position relative to one another by more than just one terrestrial minute — which is why I don't think this is a matter of simply counting backwards by 2,665.4 years. Especially since a "light year" is in reference to Earth.... heh, heh, heh....
Oh... and don't forget that hard-science tag....