  Estimating the age of the Universe is an old problem. Rapid progress in
observational cosmology in recent years has led to more accurate values of the
fundamental parameters. The current most popular model is a flat Universe, with
about 30% of the critical density in the form of matter (baryonic and
non-baryonic) and 70% in the form of `dark energy'. These two densities,
together with the Hubble constant (estimated to be about 70 km/s/Mpc),
constrain the age of the Universe to be approximately 13 Gyr. This expansion
age is uncomfortably close to the age of the oldest globular clusters
(approximately 12.5 Gyr), in particular if they formed relatively recently. We
review here proposed models of globular cluster formation and point out
possible conflicts with cosmology.
