Look-back time to the peak of the secular SFH () as a function of look-back time to the last episode of star formation (), color-coded according to Δ(age) for models with younger ages than the age of the Universe at redshift z = 0.55. As discussed in Sect. 5.2.2, contour lines indicate the level for which we can reliably assess a value of Δ(age) ≠0 at different S/N_I, obs. In particular, the threshold is Δ(age) = 0.7 at S/N_I, obs = 10 (black dashed-dotted line), Δ(age) = 0.4 at S/N_I, obs = 20 (black dashed line), and Δ(age) = 0.3 at S/N_I, obs = 30 (black solid line), respectively.