Re: Timeline of Nolan's trilogy.
I've read on numerous things that The Dark Knight takes place 6 months after the ending of Batman Begins.
The Dark Knight Rises is 8 years after The Dark Knight. I think both of these time gaps are Word of God from Nolan, but it's possible they were just written by people involved in the productions and Nolan himself could care less about assigning specific time frames to the movies.
The times are probably quite malleable so 6 months to a year between TDK and Begins and maybe more or less than 8 between TDK and TDKR.
In-film things matter somewhat but as far as I know most people write off the ages of Gordon's children in Begins as a continuity error. And assigning dates in the real world to these movies doesn't make sense to me either--Batman is always supposed to take place in the near future, to me. Batman Begins takes place several years from now, into perpetuity.