I'm part of the staff at Project Pokemon! Smod in forums, AOP in IRC, Administrator on Shoddy. Come visit us. Our Project is Pokemon!
The best way I could put the time is
Generation 1 is first of course
now I'm gonna go out on a limb and say that R/S/E happened either between Kanto and Johto or between Johto and Sinnoh, its weird because Steven shows up in HG/SS and you inherit his Villa in D/P/Pt, an educated guess would say between Johto and Sinnoh due to the Red Gyarados, which happens in Johto, which happens 3 years after Kanto, and its references in D/P/Pt. That and given the "Trade event" in FR/LG is one sided as there are no references in R/S/E
Now the 4th Gen games I believe happened around the same time, or no more than a year or two apart, again because of the "Red Gyarados" references and the fact that Professor Oak seems to be looked up to by both Prof Elm and Rowan as a higher authority figure, not to mention hes a radio celeb as well
as for 5th Gen, Unova is so far away that it could've happened at any time, but given that Cynthia is referred to simply as "PKMN Trainer Cynthia" and the fact that she mentions the Giratina event at Mt. Cornet this leads me to believe that it takes place some time in the future
and BW2 of course is just a sequel,
Last edited by red2000; 14th September 2012 at 12:55 AM.
I mean, it could appear once every month or something like that, and Jubilife TV may have reported an appearance that happened before the HG/SS player character got to the Lake of Rage.