There have been various Dark Ages (e.g. collapse of the Egyptian Old Kingdom) so it would not be the 2nd. A"Dark Age" might be defined as a loss of information & knowledge, plus a loss of population & average life expectancy and significant loss of economic & material production. This could happen as a result of a number of scenarios. read more
The Second Dark Ages for most of the United States of America alledgely started on September 11, 2001 when the World Trade Center in New York City was destroyed and will probably not end until the year 2045 or even further when the Singularity become more than just a distant fantasy or an impossible dream. read more