We rarely know the exact date and time an entire species goes extinct, but in the case of the passenger pigeon, we do. Martha, the very last of her species, took her final breath at the Cincinnati Zoo on September 1st 1914, marking the end of a species that was once the most abundant in North America. This was America's first infamous extinction.
In 2014 there are more nuclear weapons than ever, but we don't really talk about them very much. Instead we talk, primarily about the possibility of human extinction due to climate change, food shortages, ocean acidification or, occasionally, super-volcanos or comet collisions. All of these things are possible, and all of them are very unlikely to cause the extinction of humanity.