How Old is the Universe?

A dynamical model of the decaying vacuum energy is presented, which is based on Jordan-Brans-Dicke theory with a scalar field $\varphi$. The solution of an evolutionary differential equation for the scalar field $\varphi$ drives the vacuum energy towards a cosmological constant at the present epoch that can give for the age of the universe, $t_0\sim 13.5$ Gyr for ${\mathrm{\Omega }}_0=1$, which is consistent with the age of globular clusters.