The NTP software package, the official reference implementation of the NTP
protocol.
NTP is a protocol designed to synchronize the clocks of computers over a
network. NTP version 3 is an internet draft standard, formalized in RFC
1305. NTP version 4 is a significant revision of the NTP standard, and is
the current development version, but has not been formalized in an RFC.
Simple NTP (SNTP) version 4 is described in RFC 2030.