  Old high-$z$ galaxies are important tools for understanding the structure
formation problem and may become the key to determine the ultimate fate of the
Universe. In this {\it letter}, the inferred ages of the three oldest galaxies
at high redshifts reported in the literature are used to constrain the first
epoch of galaxy formation and to reanalyse the high-z time scale crisis. The
lower limits on the formation redshift $z_f$ depends on the quantity of cold
dark matter in the Universe. In particular, if $\Omega_m\geq 0.37$ these
galaxies are not formed in FRW cosmologies with no dark energy. This result is
in line with the Supernovae type Ia measurements which suggest that the bulk of
energy in the Universe is repulsive and appears like an unknown form of dark
energy component. In a complementar analysis, unlike recent claims favoring the
end of the age problem, it is shown that the Einstein-de Sitter model is
excluded at high-z by $\sim 3\sigma$.
