  The recent Gaia Data Release 1 of stellar parallaxes provides ample
opportunity to find metal-poor main-sequence stars with precise parallaxes. We
select 21 such stars with parallax uncertainties better than
$\sigma_\pi/\pi\leq0.10$ and accurate abundance determinations suitable for
testing metal-poor stellar evolution models and determining the distance to
Galactic globular clusters. A Monte Carlo analysis was used, taking into
account uncertainties in the model construction parameters, to generate stellar
models and isochrones to fit to the calibration stars. The isochrones which fit
the calibration stars best were then used to determine the distances and ages
of 22 globular clusters with metallicities ranging from -2.4 dex to -0.7 dex.
We find distances with an average uncertainty of 0.15 mag and absolute ages
ranging from 10.8 - 13.6 Gyr with an average uncertainty of 1.6 Gyr. Using
literature proper motion data we calculate orbits for the clusters finding six
that reside within the Galactic disk/bulge while the rest are considered halo
clusters. We find no strong evidence for a relationship between age and
Galactocentric distance, but we do find a decreasing age-[Fe/H] relation.
