The Hubble Space Telescope UV Legacy Survey of Galactic Globular
  Clusters. XXII. Relative ages of multiple populations in five Globular
  Clusters
  Aims. We present a new technique to estimate the relative ages of multiple
stellar populations hosted by five globular clusters: NGC 104 (47 Tuc), NGC
6121 (M4), NGC 6352, NGC 6362 and NGC 6723. Methods. We used the catalogs of
the database "HST UV Globular cluster Survey (HUGS)" to create color-magnitude
and two-color diagrams of the Globular Clusters. We identified the multiple
populations within each globular cluster, and we divided them into two main
stellar populations: POPa or first generation (1G) and POPb, composed of all
the successive generations of stars. The new technique allows us to obtain an
accurate estimate of the relative ages between POPa and POPb. Results. The
multiple populations of NGC 104 and NGC 6121 are coeval within 220 Myr and 214
Myr, while those of NGC 6352, NGC 6362 and NGC 6723 are coeval within 336 Myr,
474 Myr and 634 Myr, respectively. These results were obtained combining all
the sources of uncertainties.
