How is the story told in Chapter 9 ? (Gatsby)
The significant time jump of two years demonstrates how Nick, the meta-author as it were, is reflecting on Gatsby's life and his own personal situation. One could suggest that in Nick's reflection he shows how Gatsby's idealism lead him inevitably to this end. This shows how by two years elapsing Nick can look back in retrospect at Gatby's life and be both critical and reasonable.
Anyone else care to venture more thoughts? I've found one way :P