Left: Relative difference between the time at which the galaxy assembles its first 10⁸M_⊙ with respect to the fiducial one (synthesizer - 2 POP). Right : same as left panel but for t(10⁹ M_⊙). In both panels, smaller points are individual galaxies, bigger points with the error bars are the median obtained in each bin. The bins have been chosen to contain the same number of galaxies.