The Year 2000. Flying cars, androids, faster-than-light space travel... oh wait, we don't have any of that yet. On the plus side, our computers didn't explode, after all.
While New Year's 2000 came in with a bang, the attitudes of The '90s mostly lingered for the first year. For the United States (and arguably to a lesser extent, the world), the decade politically started on September 11th, 2001, with the terrorist attacks on New York City and Washington, D.C., which not only launched America into two wars, but continues to be a lingering specter in global politics. It is possible this decade may have ended culturally and politically in 2008–09, which saw the start of the worst economic crisis since The Great Depression, followed two months later by the election of Barack Obama as President, the mass adoption of smartphones after the release of the iPhone, as well as Facebook surpassing MySpace in traffic, "electropop era" music like Lady Gaga, Justin Bieber, and Katy Perry becoming popular, and the beginning of modern superhero blockbuster films such as the beginning of the MCU with Iron Man 1 and Christopher Nolan's The Dark Knight. Alternatively, the political end of the decade may have been in 2011, the year of The Arab Spring, Occupy Wall Street, and the death of Osama bin Laden. Culturally, the decade began somewhere around 1998-2003 with the continued rise of the internet, online music downloads, and reality shows, and ended somewhere around 2008-2013 with the rising prominence of smartphones and social media sites like Twitter, Instagram, and Facebook becoming very popular. Depending on who you ask, it may have officially ended around early 2007, when memes made their way to solid popular culture status. Either way, the transitional period in was about 1998-2003, and the transitional period out was around 2008-2013. On a Bookend manner, the zeitgeist of the 2000s started and ended with crashes on a September day in New York; literally in 2001 with the destruction of the Twin Towers, and metaphorically in 2008 with the stock market crash and the collapse of the Lehman Brothers.