Usenet (the early online discussion network) saw a rush of new American users each September, when a new crop of students began university or college. But from 1993 on, the September never ended.
Usenet began in 1980, at a time when the Internet was more like a small town than a vast ocean. Some of the first significant sites of online discussion were on Usenet. If you doubt its importance to the history of the Internet (which you shouldn’t!), Usenet is the source or the chief populariser of terms like FAQ and sockpuppet; the first commercial spam was on Usenet; when Tim Berners-Lee invented the World Wide Web he announced its creation on Usenet; when Linus Torvalds began Linux, he first shared it with the world via Usenet.
(I encountered Usenet as a teenager, specifically the newsgroup for fans of The Simpsons called alt.tv.simpsons. The character called the Comic Book Guy is a parody of the typical participant in that newsgroup.)
Because many of the early users operated out of American colleges and universities, September was a bumper month for new members. And they all had to learn the right way to interact on Usenet, picking up the customs, the slang, and the etiquette (such as it was) by trial and error. September was their learning curve, and it was also a rather trying time for the existing residents who had to help them acclimatise. But all that changed in 1993.
America Online (AOL), a major early Internet service provider, decided to add a feature that let their customers post to Usenet. The feature was added in March, and the change soon became obvious: it was like the September rush, but every month. A constant stream of new users, all unaccustomed to the sometimes esoteric and often exclusive culture of Usenet. An interstate highway had just opened up through the small town. For the “locals,” September would never end.
[Thanks to an anonymous reader for suggesting this topic.]