A glass is a peculiar, yet abundant, phase of matter. Glasses form, for example, when a liquid undergoes rapid cooling which prevents it from crystallizing. In glasses the response of macroscopic quantities (e.g. volume,  friction coefficients, dielectric constants,  etc.) to a change in conditions (e.g. temperature,  stress, electric field) easily reach astronomical time scales.  In particular, an abrupt change of several degrees will cause the volume of a glass to relax at time scales ranging from seconds to years. This volume relaxation is highly nonlinear, roughly logarithmic in time and exhibits very long time memory effects. We propose a solvable simple nonlinear equation to model this "glassy" behavior. This equation is shown to fit accurately a large body of experimental data. The results of this analysis indicate that the slowness of these structural changes in glasses has its origin in thermal activation over volume-dependent barriers.