  Due to the computational cost of calculating a great number of variations of
the parameters, detailed radiative models of pulsar wind nebulae (PWNe) do not
usually contain fitting algorithms. As a consequence, most of the models in the
literature are, in fact, qualitative fits based on visual inspection. This is
particularly true when complex, time-dependent models are considered. Motivated
by improvements in the computational efficiency of the current PWN models that
were obtained in the last years, we here explore the inclusion of automatic
fitting algorithms into a fully time-dependent model. Incorporating an
efficient fitting tool based on the Nelder-Mead algorithm, we blindly find
fitting solutions for the Crab nebula and 3C 58 with a time-dependent radiation
model to compute the spectral and dynamical evolution of young and middle-aged
PWNe. This inclusion allows us, in addition of more faithfully determining the
quality of the fit, to tackle whether there exist degeneracy in the selected
PWNe models. We find both for Crab and 3C58, that the fits are well determined,
and that no other significantly different set of model parameters is able to
cope with experimental data equally well. The code is also able to consider the
system's age as a free parameter, recursively determining all other needed
magnitudes depending on age accordingly. We use this feature to consider
whether a detailed multi-frequency spectra can constrain the nebula age,
finding that in fact this is the case for the two PWNe studied.
