  We extend to lower metallicities recent evolutionary computations devoted to
Magellanic Clouds stars, presenting and discussing new stellar models with
Z=0.0002, 0.0004, 0.0006, 0.001 and suitable assumptions about the original He
content. As in the previous paper, evolutionary results are compared with
observational data to properly calibrate the assumptions about the efficiency
of the surface convection. On this basis, we follow the evolution of stellar
models in the mass range 0.6 to 11Mo from the Main Sequence (MS) to the C
ignition or the onset of thermal pulses in the advanced Asymptotic Giant Branch
(AGB) phase, presenting cluster isochrones covering the range of ages from 20
Myr to 20 Gyr. Selected predictions constraining the cluster ages are
discussed, presenting a calibration of the difference in magnitude between the
luminous MS termination and the He burning giants in terms of the cluster age.
Both evolutionary tracks and isochrones are available at the URL
http://astro.df.unipi.it/SAA/PEL/Z0.html. Data files are also available at the
CDS.
