NTP

from The Free On-line Dictionary of Computing (8 July 2008)

Network Time Protocol
NTP

   (NTP) A {protocol} built on top of {TCP/IP} that assures
   accurate local timekeeping with reference to radio, atomic or
   other clocks located on the {Internet}.  This protocol is
   capable of synchronizing distributed clocks within
   milliseconds over long time periods.  It is defined in {STD}
   12, {RFC 1119}.