The HST UV Legacy Survey of Galactic Globular Clusters (PI: G. Piotto) collected photometric data with UV/blue filters, that are sensitive to variations in CNO abundances. Combined with previous HST optical data, it produces an unprecedented photometric database for GCs. This work presents a study of six bulge GCs, three moderately metal-rich ([Fe/H] ~ -0.5) and three moderately metal-poor ([Fe/H] ~ -1.0). By means of isochrone fitting using a Bayesian approach, we derive self-consistent accurate ages, distances, reddening, and fractions of first-generation stars. We are able to distinguish the multiple stellar populations from the Main Sequence to the Red Giant Branch. Ages are derived for the identified populations, and we investigate whether there occurs any detectable age difference between them.