• Requirement

    Provide a system capability that compares and synchronizes internal system clocks with an authoritative source to generate time stamps for audit records.

  • Discussion

    Internal system clocks are used to generate time stamps, which include date and time. Time is expressed in Coordinated Universal Time (UTC), a modern continuation of Greenwich Mean Time (GMT), or local time with an offset from UTC. The granularity of time measurements refers to the degree of synchronization between system clocks and reference clocks, for example, clocks synchronizing within hundreds of milliseconds or within tens of milliseconds. Organizations may define different time granularities for different system components. Time service can also 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. This requirement provides uniformity of time stamps for systems with multiple system clocks and systems connected over a network.

More Info

  • Title

    Authoritative Time Source
  • Domain

    Audit and Accountability
  • CMMC Level

  • Related NIST 800-171 ID

  • Related NIST 800-53 ID


  • DoD Scoring Methodology Points


  • Reference Documents

    • N/A

  • Further Discussion

    Each system must synchronize its time with a central time server to ensure that all systems are recording audit logs using the same time source. Reviewing audit logs from multiple systems can be a difficult task if time is not synchronized. Systems can be synchronized to a network device or directory service or configured manually.


    You are setting up several new computers on your company’s network, which contains CUI. You update the time settings on each machine to use the same authoritative time server on the internet [b,c]. When you review audit logs, all your machines will have synchronized time, which aids in any potential security investigations.

    Potential Assessment Considerations

    • Can the records’ time stamps map to Coordinated Universal Time (UTC), compare system clocks with authoritative Network Time Protocol (NTP) servers, and synchronize system clocks when the time difference is greater than 1 second [c]?
    • Does the system synchronize internal system clocks on a defined frequency [c]?

NIST 800-171A Assessment Guidance

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