H₀ versus age for the sample of 24 old GCs. The ages and corresponding H₀ estimates are shown as Gaussians peaked on the best-fit values and 1-σ equal to the relative uncertainties. The 1-σ limits are also highlighted in a darker blue. The solid black curves correspond to the average GC’s age and relative H₀ estimate. For comparison, the values from Riess et al. (2022) and Planck Collaboration VI (2020) are represented, respectively, with dashed and dotted lines in the H₀ domain, and in the age-domain we report the corresponding ages of the Universe as computed in a flat ΛCDM with Ω_M = 0.3 and Ω_Λ = 0.7.