  In the past 40 years a considerable effort has been focused in determining
the age of the Universe at zero redshift using several stellar clocks. In this
review I will describe the best theoretical methods to determine the age of the
oldest Galactic Globular Clusters (GC). I will also argue that a more accurate
age determination may come from passively evolving high-redshift ellipticals.
In particular, I will review two new methods to determine the age of GC. These
two methods are more accurate than the classical isochrone fitting technique.
The first method is based on the morphology of the horizontal branch and is
independent of the distance modulus of the globular cluster. The second method
uses a careful binning of the stellar luminosity function which determines
simultaneously the distance and age of the GC. It is found that the oldest GCs
have an age of $13.5 \pm 2$ Gyr. The absolute minimum age for the oldest GCs is
10.5 Gyr and the maximum is 16.0 Gyr (with 99% confidence). Therefore, an
Einstein-De Sitter Universe ($\Omega=1$) is not totally ruled out if the Hubble
constant is about $65 \pm 10$ km s$^{-1}$ Mpc$^{-1}$. On the other hand, the
newly discovered red elliptical 53W069 ($z=1.43$) provides an stronger
constraint since its minimun age is 3.2 Gyr, thus ruling out an Einstein-De
Sitter Universe unless the Hubble constant is $\leq 45 \pm 10$ km s$^{-1}$.
Using 53W069 we find an age at $z=0$ of $13 \pm 2$ Gyr, in excellent agreement
with the GC determination.
