NTP stands for Network Time Protocol. It is an application layer protocol.

Network Time Protocol (NTP), discussed in RFCs 1305 and 2030, provides a distributed mechanism for synchronizing the system clocks on computers across a network.
Sites for NTP client software should be submitted to Computers/Software/Internet/Clients/Time while sites describing NTP server software or sites from companies which provide equipment to support the protocol should be submitted to Computers/Software/Internet/Servers/Time. Sites which discuss other aspects of time and sites which display the current time from the web should be placed in Reference/Time.