Douglas Adams was right: Grammar is the biggest barrier to time travel. However, this pronoun scheme might help:
- Add suffix [-past] when addressing anyone from your relative past in the presence of their present selves
- Add the suffix [-future] when addressing anyone from your relative future in the presence of their present selves.
- If you meet two versions of yourself from the relative past or future, add the suffix [-past'] or [-future'] to whoever is from further into the past or future.
For example: If I ran into my past self, I could greet him with "Hello, me-past!" Being a savvy time traveler, the past version of me would realize I'm his future self and reply with "Greetings, me-future!" If a version of me from my relative future showed up, I would address him as "me-future," while I-past would refer to him as me-future'.
Verb tenses, however, are another ball game entirely.