Relation between ﹩{t}_{\mathrm{PM}}^{{lb}}﹩ (the age of a stream estimated using proper motions) and ﹩{t}_{\mathrm{tidal}}^{{lb}}﹩ (the age inferred from tracing star particles backward in time) for the simulations performed in this work. The vertical error bars represent the difference in measuring ﹩{t}_{\mathrm{tidal}}^{{lb}}﹩ using either 2r_t or 5r_t as the critical radius for escape. The horizontal error bars represent the uncertainty in estimating the age using Equation (5) after propagating through the typical errors with which proper motions and parallax would be measured by Gaia given the apparent magnitudes of the tracer stars in each simulation. The color scale on the right indicates the number of tracers used to estimate the age.