Globular cluster age distributions in the MW from Forbes & Bridges (2010), Dotter et al. (2010, 2011), VandenBerg et al. (2013), and Cabrera-Ziri & Conroy (2022), split up according to their likely progenitors from Forbes (2020). The shown classifications are the MW, GSE, unassociated high-energy GCs (H-E), unassociated low-energy GCs (L-E, which was given the name Koala by Forbes 2020), the Helmi Streams (H99), Sequoia (Seq), and Sagittarius (Sag). The total number of GCs in the respective sample is indicated in the top left. The distributions are computed from the GC ages and their uncertainties through a summation over normal distributions with the respective ages as the means and their uncertainties as the standard deviations. The shaded region between 8 Gyr and 11 Gyr indicates the estimated time of the GSE merger (Belokurov et al. 2018; Helmi et al. 2018). See Fig. A.6 for the corresponding histograms of the most relevant GC progenitor groups without taking the uncertainties into account.