Lewis's Notes
Writing dialogue that uses fictitious future slang is pretty fun. Coincidentally, I am taking a class on philosophy of time, which started with some readings on tense logic. This means we talk about things like the costs of endorsing a sempiternal ontology versus rejecting the implication that if it will be the case that there is someone who cures cancer, then there is someone (now) who will in the future cure cancer" (the consequent seems to suggest that whoever cures cancer is around now, the antecedent doesn't seem to require it).
"Sempiternal" is a good word because 'semp-' is a prefix meaning "always" and "eternal" means "enduring forever." "Sempiternal" is the word to use when you want to make sure there is absolutely no confusion about how long something is going to endure forever for.
Ben's Notes
So, now you know how Terror Island dialogue shifts for the past and the future. (Except in the case of demons and other supernatural creatures, who are immune to this.) We'll get into more complicated aspects eventually, but the current understanding of time should get you through most situations.