Fitting Hisui and Ingo Into The Timeline. AKA Please Stop Calling Hisui Ancient - It's Barely Even Antique
I am going to try to piece together as close as I can to the "official" timeline regarding Ingo and his excursion to Hisui, putting Hisui into its correct time context by mapping the timeline as equivalent to our world (because I've seen too many people use the word ancient to describe a time period with portable 35mm cameras). If you don't agree with that method, you won't be alone, but dead pidove: don't eat, or at least don't send hate my way about it.
Preface: feel free to take as much as you like from this, since a lot of the information is implied/deduced, not confirmed, but don't get upset at others over their opinion. If you like angst or Hisui being ancient, then keep making AUs - they're fun! Please note that angst makes me sad and I don't particularly care for the immortal Volo headcanon, so this timeline is not going to be free from bias.
Also: be wary of minor, non-plot-related ZA spoilers
1. When (in our world equivalent (owe) years) is PLA set?
Finding an upper limit for this will be quite difficult, since it would be based (for me, at least) on the absence of specific building styles or technologies. In B2W2's memory link, Drayden states "When I was little, Poké Balls didn't exist yet.", meaning that pokéballs only made it to Unova within his lifetime. This suggests that technologies in the pokémon world did not propagate quickly, so the absence of a technology in Hisui is relatively meaningless, especially since Jubilife Village is a new colony.
A lower limit is easier, though. Thanks to this post by redinthesea, I was able to find the OWE camera model that Professor Laventon owns (right picture). The Leica I(A) (middle picture), first released in 1925, looks similar, but has a reversed horizontal line on the front and three large knobs instead of two large knobs and one small knob. The Leica IB (left picture), first released in 1926, no longer has the large middle knob, so seems most similar to Laventon's.
The only cameras to feature an inverted horizontal line are copies from the 1950s to 1980s that were specifically made for left-handed people, but the buttons on the top were also inverted. I'm discounting them as the 1950s does seem a little close to the modern day, given the full-scale cities in DPP, and I'm willing to bet that the horizontal line placement is just a stylistic choice to make it more visible when Laventon holds the camera.
Conclusion: PLA is set in or after 1926 OWE
2. When are DPP set?
It is so difficult to put a year on most pokémon games, so the best we have is that DPP features references to real-world memes, including one from E3 2006 when a Galactic Grunt mentions "massive damage", so they can't be set any earlier than that. This fits with there being a wii, which came out in 2006 in the player's bedroom.
These are both likely due to Diamond and Pearl's release in 2006, but they are as good a method of dating any DS game as I could find, so until someone clowns on me with more useful information, I will attest that DPP are set in 2006 OWE or later.
3. When are BW, B2W2, and XY set?
Using the go-to sources for the timeline of the DS era, we can piece together that BW is 10 years after DPP and B2W2, which take place two years after BW take place at the same time as XY.
So the timeline looks like this so far:
PLA: 1926+ OWE
DPP: 2006+ OWE
BW: 2016+ OWE
B2W2/XY: 2018+ OWE
4. When is ZA set?
Thankfully, this one is the easiest. ZA is set 5 years after XY, so 2023+ OWE.
Added bonus because the first image I could find on google also features a reference to Leon: SWSH took place before 2023+ OWE.
It is worth noting that SWSH is set in or after 2018 OWE, as that is often cited as the year large smartphones rose to dominance. This means that ZA also can't be set before then.
5. How long is there between PLA and ZA?
2023 – 1926 = 97 years. Let's round that up to 100.
5.5. Please stop saying (ZA spoilers: if you know, you know) confirms that Volo is immortal.
It's only been 100 years, and not every collection is shown immediately, even in our world.
Calaba was 99 years old and still pretty spry in PLA, so we can assume that people are capable of lasting a little longer than in our world. Volo could have visited Kalos at age 90 or something.
Also, the building of relevance is apparently similar to the UNESCO headquarters, which opened in 1958, designwise. The other relevant building in our world opened with its current purpose in 1793, so either way you slice it, Volo could also have just visited when it opened and he was in his 50s-70s, depending on his PLA age.
There's nothing wrong with the headcanon, my point is simply that this evidence proves nothing.
6. When did Ingo leave Unova and how long was he in Hisui for?
Speaking of proving nothing, the best evidence that exists for this is Ingo's use of the phrase "Follow the rules and drive safely! We’re headed for victory! All aboard!" in Hisui, which is a direct quote of Emmet, specifically in B2W2. Obviously, Emmet could have uttered this phrase before B2W2; however, it's only used in one unique scenario, and his subway dialogue remains unchanged from BW.
This is further evidenced in ZA, as there is an npc who states that the Multi Trains are back up, suggesting that it was down recently. This could, of course, be due to maintenance.
At least we know he left Hisui from the same location in ZA that I alluded to in 5.5. For all relevant ZA screenshots I know of, check out this post by mushroomsandteeth.
Headcanon only: Ingo made a round trip sometime between B2W2 and ZA, therefore, he was gone for a maximum of 5 years.
7. TL;DR
PLA is set a maximum of approximately 100 years before ZA and Ingo likely made the round trip during the five years between B2W2 and ZA.
8. Timeline:
PLA: 1926+ OWE
DPP: 2006+ OWE
BW: 2016+ OWE
B2W2/XY: 2018+ OWE
SWSH: 2018 – early 2023 OWE
Ingo's round trip excursion: likely within 2018+ – 2023+ OWE
ZA: 2023+ OWE
9. Bonus Counter-counterarguments
I sent this post to a friend, who came up with counterarguments, so here they are, along with my thoughts. Link to search for quotes.
The clothing is 'ancient'. - Kimono exist alongside suits. This is appropriate for late Taisho/early Meiji Showa (apologies for originally writing the wrong era) era Japan.
The tech is too old-fashioned for the 1920s. - Jubilife village is a small colony that likely doesn't have easy access to technology from the rest of the world yet. Absence of 1920s tech here doesn't mean it doesn't exist elsewhere in the world.
Pokémon are only just being domesticated / people are scared of pokémon. - This is a new and small colony in an area mostly left wild by the previous colonists (the clans). It is also worth noting that the leader and several others are from towns that were destroyed by pokémon (Beni: "Kamado and I saw our hometown burned to the ground by maddened Pokémon running amok—we lost plenty of friends and comrades that day.", Jubilife Villager Ida: "I lost my home in a Pokémon attack. But then Commander Kamado kindly invited me to come here."), so I'd imagine that trauma and their stories would make it difficult to develop a culture of raising pokémon. Furthermore, Jubilife Villager Leif states, "You know, we had people back in Kanto who also were able to tame Pokémon. They knew what they were doing in battles, too." So, there is evidence that people were taming pokémon elsewhere.
The player makes the first ever pokedex. - A misconception. PLA's pokédex is the first of Hisui, but not the first, as evidenced by Laventon referencing his fellow professors when speaking of it: "We in the field call such a catalog a Pokédex. Yes, a proper Pokédex is a wonderful work of research, containing detailed records of all the Pokémon to be found in a region!".
The vibe of the world feels like a long forgotten past. - The areas outside Jubilife are mostly uninhabited due to the clans' way of life. There are ruins, which do speak of a long forgotten past, but that's so long ago in the time the game is set in that the game isn't set in that past. The only other thing I could think of to speak to this archaic vibe is the predominantly wooden housing of Jubilife Village, which is likely due to the colonists mostly coming from Japan-based regions like Kanto, Johto, and Hoenn, which may have had traditional architecture like that, and the abundance of wood in the area. The Galaxy Hall, built from red brick, stands out by design; it exists to display the might of the colonists, even if they don't have the resources to build all their houses like that. It says: "this is what we are capable of - don't mess with us."
There is no feasible way that Hisui went from wilderness to advanced cities in 100 years. - May I present Hong Kong in the 1880s vs 1975 (the building under the clock tower is being dismantled, not built). Ok, this is one city and it saw a huge amount of investment, but you absolutely can go from Brick buildings to skyscrapers in 100 years. Trade opening up within that time period would have helped to allow for some of the other improvements [e.g. Sunnyshore's solar panel walkways].
