  We calculate the expected white dwarf luminosity functions and discovery
functions in photometric passbands, if these stellar remnants provide a
substantial fraction of the sought Galactic dark matter, as suggested on
various observational grounds. We demonstrate the extremely rapid variation of
the photometic signature of halo white dwarfs with time and thus the powerful
diagnostic of white dwarf colors to determine the age of the Galactic halo. We
also consider the various indirect constraints implied by a white dwarf
dominated halo. These calculations will guide present and future observational
projects at faint magnitudes. This will enable us to determine not only the
nature of the Galactic dark matter but also the age and the initial conditions
of the Galaxy formation.
