Bulbapedia has a detailed explanation/analysis of the timeline.
The Pokémon timeline is surprisingly fun to piece together, and we have a solid understanding of it based upon in-game events and records, which was semi-officially confirmed by Toshinobu Matsumiya, who has been writing for the mainline games since Pokémon Yellow. The confirmation came in a since-deleted tweet from 2014, which plainly stated the following:
Red/Green ≈ Ruby/Sapphire → Gold/Silver ≈ Diamond/Pearl/Platinum → Black/White → Black/White 2 ≈ X/Y
From here, most games released since have very clear placements. The Legends games have a clear timeline based on premise alone— Z-A being five years after X/Y. Arceus being, obviously, hundreds of years before everything else. Sword/Shield and Scarlet/Violet are the least clear (more on that later).
For Sun/Moon, there is concept art of Grimsley stating he is two years older [than he was in BW2], indicating Gen 7 is two years after BW2/XY.
And according to An Illustrated Book of POCKET MONSTERS, Red/Green take place in 1996. This book also states that Porygon was created in 1995. This information is reconfirmed in Porygon’s Pokédex entries in Gen 7, which state it was created “roughly 20 years ago”, which also conveniently doubles as confirmation of Sun & Moon’s timeline placement.
That leaves us with a very concrete timeline, with literal dates for several of the games:
| Year |
Game(s) |
| 1996 |
Red/Green/Blue/Yellow & Ruby/Sapphire/Emerald |
| 1999 |
Gold/Silver/Crystal & Diamond/Pearl/Platinum |
| 2011 |
Black/White |
| 2013 |
Black 2/White 2 & X/Y |
| 2015 |
Sun/Moon & Ultra Sun/Ultra Moon |
| 2018 |
Legends: Z-A |
The remakes don’t necessarily adhere to the timeline. Let’s Go in particular has anachronisms. It’s pretty explicitly implied in places that the remakes exist in alternate universes. Regardless, it can be assumed they more or less correspond with their original games’ timeline placements.
It seems intentional to me that Gens 1 & 3 take place concurrently because FireRed/LeafGreen were released in Generation 3. And same for Gens 2 & 4 with HG/SS. Otherwise, it’s clear that most games are generally intended to occur in or around the same real-world year they are released. One would eagerly assume Sword/Shield must take place in 2019, then! But Legends: Z-A says Leon has already been dethroned… So Sword/Shield must occur between 2015 and 2018. As for Scarlet/Violet..? They reference Sword/Shield, so they take place after 2015. Probably 2022, if we’re being consistent. But then again, probably a different, arbitrary date.
We can therefore infer the updated timeline to (roughly) be:
Arceus → Red/Green ≈ Ruby/Sapphire → Gold/Silver ≈ Diamond/Pearl/Platinum → Black/White → Black/White 2 ≈ X/Y → Sun/Moon → Sword/Shield ≈ ZA → Scarlet/Violet
(With S/S and S/V being more of an educated guess, of course)
SOURCES (same as above links): Bulby, Grimsley, Toshimatsu-kun's forsaken tweets
