  Quantification of the Galaxy's star formation history involves both the
duration and the rate of formation, with these parameters being known with
different precision for different populations. The early rate of star formation
is knowable from modelling chemical element data, the recent rate directly from
isochrone analyses of colour-magnitude data. The field halo and globular
clusters are almost exclusively old, and formed in at most a few Gyr. The outer
bulge probably formed in a short period long ago -- extant data is
inconsistent, while the inner bulge/disk is forming today, and has continued to
form over time. Only very limited data is available on the inner disk. The
outer disk near the Sun seems as old as the halo. The earliest extended disk,
which forms the thick disk today, seems to have been in place very early, an
observation which is not simply consistent with some galaxy formation models.
