The Age of the Universe

In this article I review the main methods for determining the age of the Universe. I describe how to determine the age of the oldest known systems at z=0, the system of galactic globular clusters, using different techniques. I also describe how to date the Universe using the decay of radioactive elements (Cosmochronology). Finally, I focus on how to determine the age of the Universe at different redshifts and specially the age of radio-quiet galaxies at high redshift. I finish by arguing that the most probable age for the Universe is $14 \pm 2$ Gyr.