sntpd 3.1 sntpd is a small SNTP server and client for UNIX systems, implementing RFC 1305 and RFC 4330. Its functionality is only a small subset of ntpd, chrony, and OpenNTPd. Since it is much smaller it is also more relevant for embedded systems in need of only a background process to keep the system time in sync (client mode). HTTP Time Protocol 0.4.12 The HTTP Time Protocol (HTP) system is a set of utilities to set and maintain the system clock from the HTTP/1.1 (RFC 2616) "Date:" header.