In terms of school years:
EARLY 2010s
2009-2010 (many late 2000s influences)
2010-2011 (some late 2000s influences)
2011-2012 (few late 2000s influences & rising core 2010s influences)
2012-2013 (arguably the start of the core 2010s, no more late 2000s influences, still felt strongly early 2010s)
MID 2010s
2013-2014 (few early 2010s influences)
2014-2015 (no early 2010s or late 2010s influences)
2015-2016 (few late 2010s influences)
2016-2017 (confusing school year, late 2010s influences rising, but mid 2010s influences hanging on)
LATE 2010s
2016-2017
2017-2018 (few mid 2010s influences & no early 2020s influences)
2018-2019 (no mid 2010s influences & few early 2020s influences)
2019-2020 (rising early 2020s influences)
IMO, it would be like this:
2009-2010 (The atmosphere is noticeably entering in early 2010s territory but a lot of late 00s things are sticking around)
2010-2011 (Way more early 2010s than the previous one, some late 00s lingering but they were becoming irrelevant)
2011-2012 (The most early 2010s, almost no late 00s influences, upcoming core 2010s)
2012-2013 (Still early 2010s but declining, mid 2010s about to rise, especially in the 2013 section)
2013-2014 (Mid/core 2010s established but there were a little early 2010s hangovers)
2014-2015 (The peak of the "pure" mid 2010s, doesn't lean strongly either early or late 2010s)
2015-2016 (Still felt very mid 2010s, peak core 2010s, upcoming signs of late 2010s)
2016-2017 (Both the mid and late 2010s were at a collision course)
2017-2018 (Late 2010s but also core 2010s at the same time, probably the last)
2018-2019 (Peak of the "pure" late 2010s, almost no core influences, earliest 2020s signs)
2019-2020 (Atmosphere is still late 2010s but the early 20s were becoming more noticeable)