I was thinking about this last night and thought it might be an interesting discussion. Hopefully I can express the question in a manner that can be understood.
Imagine there’s a time traveler originating from sometime in the past. Assume this person is from a place where the latest technological innovations of his/her time are at least known, if not commonplace. This time traveler comes to what is, for us, the present. This person’s time travel lands them in a place that most of us in the “Western world” would consider to be, for the most part, technologically average, like New York City and not out in the woods in the middle of nowhere.
What is the closest approximate date (from our present) from which this person could originate and consider the present to be fantastically “futuristic,” as in a completely alien culture and technological era? The 1920s? 1910s? Civil-War era? Earlier than that?