There are two data points that I like to use to answer this question.
One is this shot from the anime. I can’t recall which episode or special or whatever it’s from, but it specifies October 1990. I can’t quite tell if it’s 21 or 31 but quite that much precision isn’t needed.
The other is the Super Famicom.
See, in the Jizō Statue arc, there’s a shot of Shampoo playing on a Super Famicom. That came out on November 21, 1990.
And you know the Jizō Statue arc is set in winter since the very plot is kicked off by a nice warm scarf.
So I may not know where along the timeline that anime screenshot is from, but I can tell you that assuming the manga itself is internally in chronological order, the second half of volume 33 is set some time but not too far after November 21, 1990, and you can work back from there.
My mission therefore: go through the manga from volume 1 to at least 33, to track the winters and figure out how many years before 1990 it started.
Lets imagine the answer is 1987. That’s when the manga first appeared in Shōnen Sunday. It ended in 1996. If the first chapter ends up being set in 1987, three years passed between 33 volumes… and six years for the last five? That can’t be right, but we’ll see!
Let’s say we assume chapter 1 is set in 1987 and count the winters up to the Jizō arc…
Okay. By my count, the story can be set in 1987 in volume 1, and have enough time pass for the SFC to come out by volume 30:
Volume 1: Manga starts publication in 1987. Volume 11: Super Soba, New Years 1988 to 1989. Volume 20: Shampoo and Maomolin, NY 1989 to 1990. Volume 30: Hinako’s Super Famicom, because there are two appearances of the damn things.
That’s counting only the volumes before #30 that have stories explicitly set on New Years, and that’s enough to make the Super Famicom fit in chronologically. It has to be at least 1990 by then, and if you count the winters it shifts up into 1991, if not later.
But! There’s a gap in my earlier conclusion, where volume 1 is in 1987 but 11 has New Years Eve 1988 to 1989. What happened to NYE 1987-88? Well, thankfully, it still works out if you count the winters. There’s two possible winters in volumes 3 and 7, with a summer in 6 and 11. Take your pick as to which of these count. If even one does, you get to 1990 in volume 20, or even as early as volume 16. Which means I need to check me some publication dates!
In terms of publication dates, volume 30 came out in 1994. Clear cut, right? First, there’s two releases. Weekly Shōnen Sunday, and the Shogakukan tankōbon. These volume numbers I’ve been using all this time are tankōbon. And those started in March 1988, not August 1987.
Easy conversion then is to subtract half a year. Okay. So the chapter with Hinako’s SFC came out early 1994 instead. Cool. Volume 1 came out in March 1988, 6 in December 1988. Volume 7 was May 1989… It’s actually pretty hard to figure this out when you don’t have publication dates for the Shōnen Sunday serialization, but clearly, the story starts in 1987, and that’s all that really matters.
And what matters to me is that enough time passes for them to have Super Famicoms.
