One thing is taking I to consideration that ALL measurements are down to human calculations so an alien species might have worked it out entirely differently.I might have missed something but a light year is "a unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km (nearly 6 trillion miles). ". Earth "only" travels about 584 million miles (940 million km) in one year. But maybe you could spin your theory taking advantage of the fact that 1 light year is the same for all species?
A technological advances alien species discovers something which is far beyond our understanding it could render our calculations invalid, we see this white a lot where science today shows science yesterday was not right and is corrected.