Hmm, I'm not sure where exactly, though maybe around BW2, but maybe during the 3 year period? I kind of imagine this region farther away so we might not even have any clue at all as to where this is.
Since the regions and all the characters are usually completely different I haven't actually spent time thinking about the overall timeline, since each could almost be happening at the same time, since each has different characters. (HGSS/DPPt/BW) Is there really a definite way to put these all together with such little evidence? I guess it's kind of like Zelda's screwy timeline, though in a different way for me I guess.