  In this paper we review the partitioned and partition-free approaches to the
calculation of the time-dependent response of a molecular junction to the
switch-on of an arbitrary time-dependent bias. Using the non equilibrium
Green's function formalism on different time contours, we derive a formal
equivalence between these two approaches. This clarifies a recent result of
[PRB 95, 104301 (2017)], which is valid for a static bias and single level
molecular structure, and extends it to arbitrary time-dependent biases and
arbitrarily large molecular structures.
