  We report on the design and performance of the electromagnetic calorimeter
timing readout system (EMTiming) for the Collider Detector at Fermilab (CDF).
The system will be used in searches for rare events with high energy photons to
verify that the photon is in time with the event collision, to reject cosmic
ray and beam halo backgrounds, and to allow direct searches for new heavy
long-lived particles that decay to photons. The installation and commissioning
of all 862 channels was completed in Fall 2004 as part of an upgrade to the Run
II version of the detector. Using in-situ data, including electrons from W=>e
nu and Z => ee decays, we measure the energy threshold for a time to be
recorded to be 3.8 \pm 0.3GeV in the central portion of the detector and 1.9
\pm 0.1 GeV in the plug portion. Similarly, we measure a timing resolution of
600 \pm 10 ps and 610 \pm 10 ps for electrons above 10 GeV and 6 GeV
respectively. There are very few system pathologies such as recording a time
when no energy is deposited, or recording a second, fake time for a single
energy deposit.
