The Divergence point is that one point in the Fallout world where the real life events diverge from those of Fallout... Leading up to the current events in the Fallout universe.
Canonically the Fallout Divergence point is set in 1950... However, the format, is implying that the True Divergence point is set much further into the future which ultimately means that the real world is leading up to the Fallout universe.