NTP

Two machines may have network connectivity, yet TLS still complains about certificate time. The logs of the same request may appear in the wrong order across different services. A device may come back online after a reboot and behave badly for a few minutes before it slowly settles back to normal time. Time looks like one of the most stable things in a system, but in distributed systems and networked devices the real question is often not “what time is it now?” It is “why should this machine trust its own clock?”