  We derive an Ito stochastic differential equation for entropy production in
nonequilibrium Langevin processes. Introducing a random-time transformation,
entropy production obeys a one-dimensional drift-diffusion equation,
independent of the underlying physical model. This transformation allows us to
identify generic properties of entropy production. It also leads to an exact
uncertainty equality relating the Fano factor of entropy production and the
Fano factor of the random time, which we also generalize to non steady-state
conditions.
