Median age–redshift trend for the 39 CCs sample, obtained with binning A. Red and blue dots represent median values, respectively, for the high-mass (log(M_formed/M_⊙) > 11.26) and the low-mass (log(M_formed/M_⊙)≤11.26) sample. In the background, grey dots are the 39 single measurements, while lines show, for illustrative purposes only, the theoretical trends with different redshifts of formation, as given by a flat ΛCDM model with Ω_M = 0.3, Ω_Λ = 0.7 and H₀ = 70 km s⁻¹ Mpc⁻¹.