Infall time versus average stellar age of the dynamically cold disk in TNG50 cluster galaxies as a function of galaxy stellar mass. We show the density contours of infall time versus stellar age of the dynamically cold disk (top panel) and versus the average stellar age of the whole galaxy age (bottom panel). Different galaxy mass bins, log₁₀M_*/M_⊙ ∈ [8,  8.6], [8.6, 9.2], [9.2, 10], and [10,12] are shown from left to right. The dashed line in the first mass bin [8, 8.6] represents its linear fit, repeated for comparison for the higher-mass galaxies. Shaded regions represent the galaxy-to-galaxy variation, i.e., the scatter to the linear fit.