  The rest-frame UV contains the most sensitive indicators of age for
elliptical galaxies. While the near-UV flux from young ellipticals isolates the
main sequence turnoff, the far-UV flux in old ellipticals is dominated by hot
horizontal branch (HB) stars. This evolved population was first revealed by
early UV observations showing a sharp flux increase shortward of rest-frame
2500 A, subsequently dubbed the "UV upturn." The phenomenon has since been
characterized in many local ellipticals, and measurements at intermediate
redshifts are now underway. Once ellipticals reach ages of 5-10 Gyr, stellar
and galactic evolution theories predict that the UV-to-optical flux ratio can
increase by orders of magnitude over timescales of a few Gyr, making the UV
upturn the most rapidly evolving feature of these galaxies. It is thus expected
to fade dramatically with increasing redshift.
  I review the imaging and spectroscopic evidence for the nature of the UV
upturn in nearby ellipticals, and then present observations that measure the UV
upturn at an epoch significantly earlier than our own. Far-UV data from the HUT
demonstrate that the spectra of nearby ellipticals are dominated by hot HB
stars. FOC UV imaging of M32 and the M31 bulge detected the UV-bright phases of
post-HB stars, but did not reach the HB itself. Recent STIS observations were
the first to image the hot HB and post-HB stars in the center of the nearest
elliptical galaxy, M32; these observations also show a striking lack of
UV-bright post-AGB stars. FOC observations of Abell 370, a rich galaxy cluster
at z=0.375, show that giant ellipticals at a lookback time of 4 Gyr can exhibit
strong UV luminosity, with no evidence of evolution in the UV upturn between
this epoch and our own, thus implying a high redshift of formation (z_f > 4).
