This is the sort of thing that I love reading on the internet.

Sorry to disappoint you, but most of that text is found offline — as it's an excerpt from Douglas Adam's "The Restaurant at the End of the Universe" (sequel to "The Hitchhiker's Guide to the Galaxy"). I probably should've attributed it.

If only doing things from the PoV of the speaker (you), that means 6~9 tenses for what most languages have 2 (past and non-past) or 3 (past, present, future).

And then you'd have to account who knows what, which version of a person you're talking to. Say you're having a conversation with someone before traveling in time to a time in which they've not timetraveled, so it's either their subjective past or future, but then you continue the conversation, so you'd have to account for both the speakers perspective and the person being spoken to, who would then be subject to two different tense "totalities" since the conversation with them would have been taking place in two different times at the same time.

I seriously suggest reading Douglas Adams and Terry Pratchett for that sort of thing. I used to use Pratchett books as a substitute for weed when I was a bit over twenty.