  This paper discusses the design and performance of the time measurement
technique and of the synchronization systems of the CMS hadron calorimeter.
Time measurement performance results are presented from test beam data taken in
the years 2004 and 2006. For hadronic showers of energy greater than 100 GeV,
the timing resolution is measured to be about 1.2 ns. Time synchronization and
out-of-time background rejection results are presented from the Cosmic Run At
Four Tesla and LHC beam runs taken in the Autumn of 2008. The inter-channel
synchronization is measured to be within 2 ns.
