I don't know exactly when they came into being. I know that they had already been in for quite a while before I joined back in 1987, so they've been going for a long time now. They've gone through some major policy changes. Up until a few years ago, DCO was actually working with individual defence force members, but then they changed their policy and said they're only working with the families of the defence force members.
On February 28th, 2011. See this statement in context.