to read the current documentation, applicable to NTP version 4.2.8 through 4.2.8p15.
Archived documentation for older major NTP releases is available:
applicable to NTP version 4.2.6 through 4.2.6p5.
applicable to NTP version 4.2.4 through 4.2.4p8.
applicable to NTP version 4.2.2 through 4.2.2p4.
Whitepapers, RFCs, and other technical documents written by Professor David L. Mills, inventor of NTP.
Frequently Asked Questions about the NTP protocol and software distribution.
Public Time Server Lists:
Browse or search for a public primary or secondary time server.
NTP Google group:
Includes postings from original Usenet newsgroup going back to June, 1990.
Network Time Foundation