Quoted By:
Do we have any frame of reference as to how long SwSh and SV took place after SM/USUM?
Johto/Sinnoh takes place 3 years after Kanto/Hoenn, this is explicitly stated.
Unova takes place roughly 8 years after Johto/Sinnoh, eyeballing this solely based on Caitlin's age in BW comparted to that in HGSS and Platinum.
Unova2 takes place 2 years after Unova, this is explicitly stated
Kalos takes place around the same time as Unova2, judging by the TV broadcast at the start.
Alola takes place 2 years after Kalos and Unova2, this is coming from a guidebook saying Grimsley's appearance takes place two years after BW2.
But we have no frame of reference for Galar and Paldea,
Also I'm completely making a guess on the Orre games here. I just like to think XD lines up with Johto/Sinnoh because of Bonsly and Munchlax's appearances, which is weak but still. If you have a better idea, please tell me.