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The orbit distribution of young stars in the Galactic disk is highlystructured, from well-defined clusters to streams of stars that may be widelydispersed across the sky, but are compact in orbital action-angle space. Theage distribution of such groups can constrain the timescales over whichco-natal groups of stars disperse into the `field'. Gaia data have provenpowerful to identify such groups in action-angle space, but the resultingmember samples are often too small and have too narrow a CMD coverage to allowrobust age determinations. Here, we develop and illustrate a new approach thatcan estimate robust stellar population ages for such groups of stars. Thisfirst entails projecting the predetermined action-angle distribution into the5D space of positions, parallaxes and proper motions, where much larger samplesof likely members can be identified over a much wider range of the CMD. It thenentails isochrone fitting that accounts for a) widely varying distances andreddenings; b) outliers and binaries; c) sparsely populated main sequenceturn-offs, by incorporating the age information of the low-mass main sequence;and d) the possible presence of an intrinsic age spread in the stellarpopulation. When we apply this approach to 92 nearby stellar groups identifiedin 6D orbit space, we find that they are predominately young ($\lesssim 1$Gyr), mono-age populations. Many groups are established (known) localizedclusters with possible tidal tails, others tend to be widely dispersed andmanifestly unbound. This new age-dating tool offers a stringent approach tounderstanding on which orbits stars form in the solar neighborhood and howquickly they disperse into the field.

The Age Distribution of Stellar Orbit Space Clumps