The Ottoman Empire ended in 1922. The Roman Empire, 476, though it was survived by the Eastern Roman Empire which lasted until 1453 and the Holy Roman Empire which stuck around in some form until 1806.
Obviously these dates are inexact, but it's a useful historical tool to pick two events and use them as bookends to describe the arc of a given empire or society.
So with the benefit of sufficient hindsight, say 500 or 1000 years from now, what do you think will be the generally accepted date printed in history books for "here's the event that signals the end of this period of history"?
Do you believe it will be some point in the past, or the future? If you think it's in the past, how far back? What event?
If you think it's in the future, how far in the future? What do you predict will happen at that time to be the historical marker?
p.s. don't say "all history will be forgotten because of nuclear war". I agree that's a distinct possibility, but the likelihood of it happening is best addressed as a separate topic from this one. for the purposes of this thread assume we haven't completely fucked ourselves as a species and at least some records of our current time period exist.