We should (have?) learn(ed?) from Douglas Adams:
The major problem [of time travel] is simply one of grammar, and the main work to consult in this matter is Dr. Dan Streetmentioner’s Time Traveler’s Handbook of 1001 Tense Formations. It will tell you, for instance, how to describe something that was about to happen to you in the past before you avoided it by time-jumping forward two days in order to avoid it. The event will be described differently according to whether you are talking about it from the standpoint of your own natural time, from a time in the further future, or a time in the further past and is further complicated by the possibility of conducting conversations while you are actually traveling from one time to another with the intention of becoming your own mother or father… The Hitchhiker’s Guide to the Galaxy skips lightly over this tangle of academic abstraction, pausing only to note that the term “Future Perfect” has been abandoned since it was discovered not to be.”
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.