  I report outcomes of the analysis of the $A^+$ parameter, which measures the
level of radial segregation of blue straggler stars in old star clusters,
commonly known as the dynamical clock for the long-term internal dynamical
evolution. I used $A^+$ values available in the literature for 48 Milky Way
globular clusters. I found that the relationship of $A^+$ and the number of
central relaxation times which have elapsed ($N_{relax}$) shows a non
negligible dependence on the strength of the host galaxy gravitational
potential, in addition to depending on the two-body relaxation mechanism.
Indeed, a measured $A^+$ value corresponds to relatively smaller or larger
$N_{relax}$ values for star clusters located farther or closer to the galaxy
center. From an observational point of view, this finding reveals the
possibility of disentangling for the first time the dynamical evolutionary
stage due to two-body relaxation and tidal effect, that affect the whole star
clusters' body concurrently.
