There are many problems currently with being able to age date a given black hole.
Firstly, the analogy of dating stars is not a good one. We date stars based upon their mass and spectral class, but this itself can be problematic, illustrated by the initial date of HD 140283 being older than that of the universe. This age was revised down, but it's still on the very edge even still. A black hole is not sustained by nuclear fusion, which follows a nice predictable chain all the way down to iron.
As mentioned above, if the black hole is sufficiently young, the nebula resulting from the supernova which created it. This problem with this is that these nebulae tend to dissipate after only a few million years. Because of this the window to date a black hole by this method is, in astronomical terms, quite narrow.
Black holes have been theorized to dissipate energy via Hawking radiation, a form of the Casimir effect. The problem with using this to date a black hole is that we have never detected it as yet (That I am aware of).
In short, the only way we can date a black hole is, fittingly, the only way we can locate them, i.e. by inference. These dates are not precise, and carry with them large error bars, and take into effect average density of stars and gas around them and how they differ from around the black hole, if the black hole is supermassive, the presence of an accretion disk / quasar, but all in all, there is no real way to date a black hole that we know of as of yet.
Sorry for the wall of text.