[Y/Mg] vs. stellar age as a test of the StarHorse ages. The stars (black dots) were selected after a cross-match with the GALAH DR3 catalogue (see text for details). The red dashed line represents the best-fit line from Nissen et al. (2020) for a sample of nearby solar twins and the orange line is our best fit for this data set. In this plot, we extend the [Y/Mg] chemical clock to the oldest ages and show that the StarHorse ages for the RVS-CNN catalogue are reliable at old ages with a good age resolution.