Originally Posted by Broker
In his first scene with the mob Joker says that -
"Let's wind back the clocks. A year ago these cops and lawyers wouldn't have crossed any of you"
That's probably the closest to a time frame but it's nothing specific still. The joker is talking in general not to mention it seems he's referring to batman's involvement in aiding the police which may have come a little later on.
It's a good start but i don't think anyone can piece together an accurate timeline aside form the known 8 years between TDK and TDKR.
Does anyone know if those newspapers in TDK had any dates on them? because i beleive TDK took place in the present ie 2008.