Quick Answer

The answer is to synchronize the FortiGate's system clock with a reliable time source. This synchronization is critical because the FortiGate uses its system clock to timestamp logs, validate digital certificates, and enforce time-based firewall policies; without an accurate clock, these security functions become unreliable or fail entirely. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this concept tests your understanding that NTP is the underlying mechanism for clock accuracy, not a policy feature itself—a common trap is confusing NTP configuration with the time-based policy feature that depends on it. Remember, NTP provides the foundation: if the clock drifts, certificate validation breaks and logs become untrustworthy. A simple memory tip is "NTP for the tick, policies for the tock"—NTP keeps the clock accurate so that time-based rules can fire correctly.