  We use the second Gaia data release in combination with the catalog of
Sanders & Das (2018) to dissect the Milky Way disc in phase-space and relative
ages. We confirm and report the existence of multiple velocity moving groups at
low azimuthal velocities and angular momenta, below Arcturus, regularly
separated by $\sim~18-20\,\rm{km s^{-1}}$ in azimuthal velocity. Such features
were predicted to exist more than ten years ago from the reaction of the Milky
Way to a perturbation in the disc undergoing phase-mixing. These structures
appear slightly younger than their phase-space surroundings, arguing against an
extra-galactic origin. We also identify in relative age many of the classical
ridges in the plane of azimuthal velocity vs. Galactocentric radius,
traditionally associated with resonance features. These ridges are also younger
than their phase-space surroundings in accordance with predictions from recent
state-of-the-art cosmological hydrodynamical simulations of Milky Way-like
galaxies. We study the response of dynamically young and old stellar disc
populations to resonances from an analytic model of a large bar, which,
remarkably, qualitatively reproduces the trends seen in the data. Our results
re-inforce the idea that the Galactic disc is currently being shaped by both
internal and external perturbations, and that, while absolute isochrone ages
have to be taken with great care, exploring the dynamical structure of the disc
in stellar ages, especially with future asteroseismic data, will provide much
stronger constraints than metallicity/abundance trends alone.
