Chrony is an implementation of the Network Time Protocol (NTP). It can synchronize the system clock with NTP servers, reference clocks (e.g. GPS receiver), and manual input using wristwatch and keyboard. It can also operate as an NTPv4 (RFC 5905) server and peer to provide a time service to other computers in the network.

Chrony consists of two programs: chronyd and chronyc.

Chronyd is a daemon which runs in the background on the system. It obtains measurements of the system clock’s offset relative to time servers on other systems via the network and adjusts the system time accordingly. For isolated systems, the user can periodically enter the correct time by hand (using chronyc). In either case, chronyd determines the rate at which the computer gains or loses time, and compensates for this. Chronyd can act as either a client or a server.

Chronyc provides a user interface to chronyd for monitoring its performance and configuring various settings. It can do so while running on the same computer as the chronyd instance it is controlling or a different computer.