Demon Answers Demon Slayer Timeline Questions, More at 1(am).
This has been sitting in my drafts for a couple wekk. Might as well get it out there, I guess.
Ladies, gents, enbies, everyone... I've done it. I have cracked the code! I have opened the vault! I KNOW WHEN DEMON SLAYER TAKES PLACE!! No clue if it's been done before, but whatever!
SO! Dumb brain decided 1 am(hence the title) was a delightful time to do some math. As ya do. Specifically, some math regarding the Hand Demon. He said he was on Mount Fujikasane for 47 years when Tanjirou confronted him during Final Selection.
Because the Meiji Era was only 44 and a half years(January 1868 to July 1912)! And the Hand Demon DOES mention being captured by Urokodaki in the Edo Period, so we know he wasn't thrown in the forest during the Meiji Era. That gives a 2.5-3 year window for him to be captured in the Edo Period and be there long enough to make it to the Taisho Era. So that drastically narrows down when he was put there, as well as when Tanjirou participated in Final Selection. By extension, narrowing down when the main series takes place!
So! I did the math and noted some other clues that give us the answer to when in the Taisho Era the bulk of Demon Slayer takes place. The post-Final Selection Arc series(flashbacks notwithstanding) should be taking place in ~1915-1916.
Another reason I say this is because of our fun little Taisho Secrets and Rumours. The Taisho Era Secrets are implemented before the 2-year time skip after Tanjirou's training, so that puts the Kamado family being attacked at the last few days or week of 1912 or 1913.
Simple, the Taisho Era didn't start until July of 1912, and context clues in Episode/Chapter 1 indicate the Kamado family got attacked around New Year's. Most likely late December. Obviously, since we're in the Taisho Era here, that means we're at the tail end of either 1912 or 1913 when Tanjirou and Nezuko's journey starts. It can't have taken them SEVEN months to reach the place they met Urokodaki at, even if they are on foot! Japan is small, in comparison to a lot of countries(For reference, it only takes ~46 days to go from Victoria, BC to Laborador City on foot. And that's as close to across Canada as I could think of off the top of my head. That's one of the biggest countries on the planet! And that doesn't even take TWO months!)!
TL;DR: Demon Slayer most likely takes place in 1915-1916, and I figured that out from a single line early in the series!
Seriously, why is it THE DEMONS giving me answers?!