HTTP Time Protocol is a time synchronization tool that uses Web server responses (HTTP headers) instead of the NTP protocol. If you are behind a corporate firewall, NAT device, or proxy server, HTP will still be able to synchronize the time. For high precision time synchronization, use ntpd.
NTPmon is a Web-based monitor for (usually LAN-based) NTP servers. It provides a small number of health metrics that help to locate NTP configuration or operational trouble spots. It uses RRDtool as its storage and graphing engine, and provides a CGI script for viewing the results.