Source : Free On-Line Dictionary of Computing

Network Time Protocol
     
        (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}.