AU.L2-3.3.7
Authoritative Time Source
Source and approval
CMMC Assessment Guide — Level 2 · Revision 2.13
Publisher approved · Complete cited source edition 2026-10-31
Read the official guideSee AU.L2-3.3.7 in the reference catalog with its NIST cross-references
Official requirement
Provide a system capability that compares and synchronizes internal system clocks with an authoritative source to generate time stamps for audit records.
Assessment objectives
a. internal system clocks are used to generate time stamps for audit records;
b. an authoritative source with which to compare and synchronize internal system clocks is specified; and
c. internal system clocks used to generate time stamps for audit records are compared to and synchronized with the specified authoritative time source.
Implementation guidance
Editorial examples to help you plan. Adapt them to your environment; the official requirement and objectives remain authoritative.
In plain language
Synchronize system clocks with an authoritative time source.
Implementation example
Example from the source assessment guide (not a mandatory implementation): 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.
Evidence examples
Examples suggested by the source guide (not an exhaustive or mandatory checklist): Audit and accountability policy; procedures addressing time stamp generation; system design documentation; system security plan; system configuration settings and associ ated documentation; system audit logs and records; other relevant documents or records
Common mistakes
Allowing inconsistent timestamps that prevent reliable event correlation.