NIST 800-53 REV 5 • AUDIT AND ACCOUNTABILITY
AU-8 — Time Stamps
Use internal system clocks to generate time stamps for audit records; and Record time stamps for audit records that meet {{ insert: param, au-08_odp }} and that use Coordinated Universal Time, have a fixed local time offset from Coordinated Universal Time, or that include the local time offset as part of the time stamp.
Supplemental Guidance
Time stamps generated by the system include date and time. Time is commonly expressed in Coordinated Universal Time (UTC), a modern continuation of Greenwich Mean Time (GMT), or local time with an offset from UTC. Granularity of time measurements refers to the degree of synchronization between system clocks and reference clocks (e.g., clocks synchronizing within hundreds of milliseconds or tens of milliseconds). Organizations may define different time granularities for different system components. Time service can be critical to other security capabilities such as access control and identification and authentication, depending on the nature of the mechanisms used to support those capabilities.
Practitioner Notes
Audit records must include accurate timestamps. If the clocks on your systems are not synchronized, you cannot correlate events across systems — and your timeline will be wrong during an investigation.
Example 1: Configure all Windows systems to synchronize time via GPO at Computer Configuration → Administrative Templates → System → Windows Time Service → "Configure Windows NTP Client". Point to a reliable NTP source. Your domain controllers should sync to an external authoritative source (time.nist.gov or GPS), and all domain members sync to the DC.
Example 2: On Linux systems, configure chrony or ntpd to sync with the same time source as your Windows infrastructure. Verify sync status with chronyc tracking or ntpstat. Monitor for time drift greater than 1 second — large drift indicates a configuration problem or a time-based attack.