  We show for the first time, that a fully cosmological hydrodynamical
simulation can reproduce key properties of the innermost region of the Milky
Way. Our high resolution simulation matches the profile and kinematics of the
Milky Way's boxy/peanut-shaped bulge, and hence we can use it to reconstruct
and understand the bulge assembly. In particular, the age dependence of the
X-shape morphology of the simulated bulge parallels the observed metallicity
dependent split in the red clump stars of the inner Galaxy. We use this feature
to derive an observational metric that allows us to quantify when the bulge
formed from the disk. The metric we propose can be employed with upcoming
survey data to constrain the age of the Milky Way bar. From the split in
stellar counts we estimate the formation of the 4~kpc scale bar in the
simulation to have happened $t^{\rm bar}_{\rm form}\sim8^{+2}_{-2}$ Gyr ago, in
good agreement with conventional methods to measure bar formation in
simulations. We test the prospects for observationally differentiating the
stars that belong to the bulge/bar compared to the surrounding disk, and find
that the inner disk and bulge are practically indistinguishable in both
chemistry and ages.
