@SmallTinyNeedles that's the year the chapter was released, it doesn't mean that the story in the manga itself is set on that year. The narration in the first chapter and in the summer holiday arc seems to imply that everything in this manga happened in the past. However, reading through the manga again I noticed that they're talking about Photoshop CS4 and PaintTool SAI which would put the timeline of the story somewhere between 2008-2010. So I think it is safe to assume that this story took place in 2008 or the same year the manga started publication.
Chapter 24 could also be a reference to 2008 stock market crash, that would put us around the end of September/early October 2008. That still fits with the timeline because not much time have passed since the end of summer vacation.