Well it's hard to say since it has some stuff that is really modern and some stuff that is really retro so I believe it depends on town you are in since Bridgeport seems to feel really modern in terms of furniture and clothing but Sunset Valley seems more retro but that's actually how it is since Sunset valley is I believe 50 years before Pleasantview (TS2). In conclusion, The Sims 3 is not stuck in 1 time period but the towns that come in the base game, expansion packs, and store are based in different time periods.
Oh, and another proof is that in Sunset Valley Bella Goth is a kid but in Lunar Lakes she is dead...
