chrony is a client and server for the Network Time Protocol (NTP). This program keeps your computer's clock accurate. It was specially designed to support systems with intermittent Internet connections, but it also works well in permanently connected environments. It can also use hardware reference clocks, the system real-time clock, or manual input as time references.
SNTS (Simple Network Time Sync) is a simple, fast, and low-overhead time syncronization system for LANs. It is designed as a simple replacement for timed with better time control and better portability (for systems without a standard adjtime() call, such as Linux). It uses broadcasts to negotiate servers and set time, and allows multiple groupings of servers on a network for independent time management for groups or labs. SNTS also supports multiple servers in a single group.