November 2000

Yep. Source: https://www.eecis.udel.edu/~mills/database/papers/nano/

Assuming the timestamps are not forged, this only shows that the paper was uploaded November 2000. It might have been older. So we need a second source.

Second source: The citations. The paper cites: "Mogul, [...] Pulse-per-second API for Unix-like operating systems [...] March 2000 [...]"

So the paper is not older than November 2000 and not younger than March 2000.

It was published at the "Precise Time and Time Interval Meeting" in November 2000 (which a footnote in nano.pdf says as well)