My opinion (USA, born 2001):
2010-2014 were really just an extension of the 2000s, with a very similar culture to the 2000s, especially the late 2000s. In terms of American politics, the post-9/11 vibe was still there, and Obama's campaign and first term (2008-12) was entirely 2000s. The Great Recession and Obama's run--both 2008 events--were major 2000s touchstones, thus setting the early 2010s up to follow in their footsteps.
2015 and 2016, especially 2016, however, is when things really started shifting, with the rise of Trump and his counterparts in other western countries. Politically, on the right, Bush-style neocon-ism rapidly falls out of style in favor of the alt-right. On the left, we start to see a bit of a countercultural revival, for the first time really since the '90s; the 2001-2014 left seemed more like a USA-style "Official Opposition" (look it up) than a true protest movement. Trump, on the other hand, was able to galvanize: (1) liberals, (2) leftists, (3) centrists, (4) neocons who hadn't defected to Trump, and (5) actually competent fascists, into a massive (but loose) anti-Trump coalition, which revitalized the old-school, pre-9/11, truly "f**k the USA" left.
2017-2019 (more specifically, January 2017-March 2020), will always be remembered as the "Pre-COVID Trump Years." Having been followed as they were by the absolute shitfire that was 2020, we'll likely look back on them with an ironic fondness for thinking, "Surely this is the worst things can get..." Little did we know of the impending pandemic (and its multifaceted-ly sh***y aftermath) in store, which would have been bad enough even if it hadn't been coupled with the murder of George Floyd and the ensuing racial justice movement, the latter of which really set the aforementioned countercultural revival on absolute fire (in some cases literally). This is when, IMO, the 2020s started, and of course they've been going on to this day.