Pop culture years often correspond with school years, meaning lots of new trends start in the Fall. For instance, MTV premiering in August of 1981, grunge in September 1991, or Britney Spears having her first hit at the very end of 1998. Summers are also traditionally "hot" periods for fashion and music, and of course, TV seasons run from Fall to Spring as well.

Do you think this is coincidental? I've often wondered about this. Like, new trends traditionally starting in the Fall because kids tend to want to get into something different when they get back to school.

Yeah, usually when a new trend starts up its later in the year, toward August or September. Usually the earlier part of a year is sort of like the previous year(for example most hit songs in the early part of the year are actually songs from albums that came out the previous year). Usually around the summer/fall is when new stuff starts to emerge.

Pop culture years often correspond with school years, meaning lots of new trends start in the Fall. For instance, MTV premiering in August of 1981, grunge in September 1991, or Britney Spears having her first hit at the very end of 1998. Summers are also traditionally "hot" periods for fashion and music, and of course, TV seasons run from Fall to Spring as well.

Yeah Britney debut on the music scene with "Baby One More Time" right before christmas time in 1998. I think the Spice Girls debut and hit big in the US late 96/early 97 maybe too start the whole late 90's/early 00's teen-pop trend.

Yes...probably the same reason that before Christmastime....all you see are new toy commercials, etc.  It's all about marketing what will be popular at a given point, that happens to be when something is turning over or changing once again.