I think all this happened just before skypea or was it just after.
We still dont know the significance of the word 'D'.
In Oda's SBS questions and answer corner, he was asked what the D in Luffy's name stood for. Oda just replied to read it as a D for now and that he would reveal the truth behind it in time.This was the first time Luffy's 'D' was brought up, as well as Oda's first hint towards a bigger mystery.