  Dark energy is the invisible fuel that seems to drive the current
acceleration of the Universe. Its presence, which is inferred from an
impressive convergence of high-quality observational results along with some
apparently sucessful theoretical predictions, is also supported by the current
estimates of the age of the Universe from dating of local and high-$z$ objects.
In this paper we test the viability of several dark energy scenarios in the
light of the age estimates of the high redshift ($z=3.91$) quasar APM
08279+5255. Using a chemodinamical model for the evolution of spheroids, we
first reevaluate its current estimated age, as given by Hasinger et al. (2002).
An age of 2.1 Gyr is set by the condition that Fe/O abundance ratio (normalized
to solar values) of the model reaches 3.3, which is the best fit value obtained
in the above reference. It is shown that for the currently accepted value of
the matter density parameter, most of the existing dark energy scenarios cannot
accomodate this old high redshift object unless the Hubble parameter is as low
as $H_o = 58$ $\rm{km.s^{-1}.Mpc^{-1}}$, as recently advocated by Sandage and
collaborators. Even considering less stringent age limits, only cosmological
models that predicts a considerably old Universe at high-$z$ can be compatible
with the existence of this object. This is the case of the conventional
$\Lambda$CDM scenario and some specific classes of brane world cosmologies.
