AU-8: Time Stamps

The AU-8: time stamps requirement means your audit logs must record reliable, consistent time using internal system clocks, so investigators can reconstruct events across systems. Operationalize it by standardizing time configuration, synchronizing clocks, defining a time source, validating log fields, and retaining evidence that clocks stay accurate and protected. ¹

Key takeaways:

• Standardize a trusted time source and ensure every in-scope system stamps audit records using its internal clock. ¹
• Prove it works with repeatable evidence: configurations, monitoring, and sample logs showing time stamp fields and time zone handling.
• Build audit-readiness by assigning a control owner, a procedure, and recurring artifacts tied to AU-8. ¹

AU-8 is a deceptively small control with outsized audit impact. If time stamps are missing, inconsistent, or drifted, you lose the ability to correlate security events, validate the sequence of actions, and support incident response or eDiscovery. Auditors also treat weak time as a systemic logging failure because it undermines every downstream detection and investigation control that depends on log integrity.

For a Compliance Officer, CCO, or GRC lead, the fastest way to operationalize AU-8 is to treat it as an engineering standard with compliance wrappers: define which systems are in scope, specify the time configuration standard (source, sync method, time zone, format), verify that audit records actually include time stamps, then collect evidence on a recurring cadence.

This page focuses on requirement-level implementation: what AU-8 requires, who owns it, the concrete build steps, and the evidence package that tends to satisfy assessors for NIST SP 800-53 Rev. 5 environments. ²

AU-8: time stamps requirement (plain-English)

Requirement intent: audit records must include time stamps generated from internal system clocks so logs reflect when events occurred, based on the system’s own timekeeping. ¹

What assessors look for in practice

• Audit logs contain a time stamp field for relevant events (authentication, admin actions, access to sensitive data, security-relevant configuration changes).
• Time is consistent across systems so cross-host correlation works (SIEM searches, incident timelines, application-to-database tracing).
• You can show how time is set, synchronized, monitored, and corrected when drift is detected.

Regulatory text

NIST SP 800-53 Rev. 5 states: “Use internal system clocks to generate time stamps for audit records; and” ¹

Operator translation: what you must do

1. Ensure every in-scope system that produces audit records relies on its internal clock to stamp those records. ¹
2. Make that internal clock dependable by managing configuration (time source, synchronization, time zone/format) and by verifying logs contain the expected time stamp fields.

Who this applies to (entity and operational context)

Entities

• Federal information systems and programs adopting NIST SP 800-53 Rev. 5. ²
• Contractor systems handling federal data where NIST 800-53 controls are contractually flowed down (common in agency ATOs and security requirements). ²

Operational scope (what systems are typically “in”)

• Identity and access systems (IdP, directory services, PAM).
• Core infrastructure (hypervisors, VPN, firewalls, EDR, email security).
• Applications that create security-relevant events (admin consoles, data access layers, API gateways).
• Central logging and analytics (SIEM, log pipelines, collectors).
• Managed services and third parties that deliver audit logs you rely on for detection or investigations (you still need to validate their time stamp behavior as part of third-party due diligence).

What you actually need to do (step-by-step)

Step 1: Assign ownership and define the AU-8 “time standard”

Create a one-page standard owned by Security Engineering or Platform Engineering, with GRC as the governance owner:

• Authoritative time source(s) (example: enterprise NTP service, cloud time sync service).
• Required time zone handling (many teams standardize on UTC for logs to reduce correlation errors).
• Required time format in logs (for example, ISO 8601 in UTC, if your tooling supports it).
• Minimum logging fields required for audit records (event time, ingest time, host identifier).

Tie the standard to AU-8 in your control matrix and evidence plan so it is assessable and repeatable. ¹

Step 2: Build the inventory of in-scope log sources

Create an “AU-8 in-scope systems” list that aligns to your audit logging boundary:

• Systems required by your AU controls (logging) and incident response program.
• Systems in your moderate/high impact boundary (or any boundary defined in your SSP).

Practical tip: start with your SIEM onboarding list, then add “dark” systems that generate logs but are not centrally collected yet (network appliances, SaaS admin consoles).

Step 3: Configure time synchronization on each platform class

For each system class, document and implement the time configuration:

• Linux: NTP/chrony config, allowed time servers, drift file handling.
• Windows: domain time hierarchy and NTP settings.
• Network devices: NTP servers, authentication if supported, time zone settings.
• Cloud: instance time sync mechanisms and constraints (some platforms discourage manual time changes).
• Containers/Kubernetes: node time config (pods inherit node time), log forwarding time field mapping.

Your goal is not perfection; it is a defensible, consistent configuration that produces trustworthy time stamps in audit records and can be proven during an assessment.

Step 4: Validate the audit record time stamp fields end-to-end

Do a functional test for each major log source type:

• Generate a known event (failed login, privilege change, config change).
• Confirm the log entry contains a time stamp derived from the system clock.
• Confirm the time stamp is parsed correctly by your SIEM (field extraction, timezone normalization).
• Confirm correlation works across at least two systems (for example, IdP event and application event align in sequence).

This is where many programs fail AU-8: they configure NTP but never verify that the audit record fields are present, consistent, and usable.

Step 5: Monitor drift and operationalize correction

Define an operational mechanism:

• Monitoring alert when a system’s time drift exceeds your internal threshold.
• Ticketing runbook to remediate time drift.
• Exception process for systems that cannot sync to the standard source (legacy, isolated networks).

You do not need a complex program to start. You need a repeatable one that produces artifacts.

Step 6: Package the control for audit readiness (evidence mapping)

AU-8 becomes easy to defend when you map it to:

• Control owner
• Written procedure
• Recurring evidence artifacts (monthly/quarterly, aligned to your audit cycle) ¹

If you use Daydream, treat AU-8 as a requirement page with assigned ownership, system scope, and an evidence checklist. The win is consistency: the same artifacts, generated the same way, every cycle. ¹

Required evidence and artifacts to retain

Keep evidence that shows design and operating effectiveness:

Design evidence (what you intended to implement)

• AU-8 time standard (time sources, timezone, format requirements).
• System configuration standards (gold images, baseline configs, infrastructure-as-code snippets).
• Architecture diagram or data flow showing log sources and central collection (helps prove end-to-end handling).

Operating evidence (what is actually happening)

• Screenshots/exports of NTP/time sync configuration for representative systems in each class (Linux, Windows, network, cloud).
• Time sync monitoring outputs or alert samples (even a small sample set is useful).
• Sample audit logs showing time stamp fields, timezone/offset, and parsing in SIEM.
• Change records for time configuration changes (approvals, deployments).

Common exam/audit questions and hangups

Expect these:

1. “Show me that audit records have time stamps.” Bring sample logs from multiple sources.
2. “What is your authoritative time source?” Point to your standard and configs.
3. “How do you detect and correct drift?” Show monitoring, tickets, and a runbook.
4. “Do third parties’ logs align with your timeline?” Show onboarding checks for SaaS/admin logs and how you normalize timestamps in the SIEM.

Hangup: assessors often reject “we set NTP everywhere” without proof that logs contain usable timestamps.

Frequent implementation mistakes and how to avoid them

Mistake	Why it fails	Fix
Relying on SIEM ingest time only	Ingest time is not event time; correlation breaks during pipeline delays	Require event-time fields from the source and validate parsing
Mixed time zones across systems	Incident timelines become error-prone	Standardize timezone handling (commonly UTC) and document it
NTP configured but not monitored	Drift accumulates silently	Add drift alerts and a remediation runbook
No evidence plan	Control “exists” but can’t be assessed	Predefine artifacts and collect them on a cadence 1
Ignoring SaaS/admin logs	Key security events happen in third parties	Include critical third parties in AU-8 scope and validate their timestamp formats

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for AU-8, so this page focuses on audit and security risk rather than case outcomes.

Risk is still concrete:

• Weak timestamps slow incident response and increase the chance you cannot prove what happened first.
• Logging and monitoring controls become harder to validate because time is the backbone of event reconstruction.
• During an assessment, AU-8 gaps often cascade into findings on related audit/monitoring controls because assessors cannot trust the audit trail.

Practical execution plan (30/60/90-day)

Use this as an operator’s checklist. Adjust to your system boundary and change control capacity.

First 30 days (Immediate stabilization)

• Assign AU-8 control owner and approver; document the AU-8 time standard. ¹
• Build the in-scope inventory of log sources (start with SIEM sources plus critical identity/admin systems).
• Collect “current state” evidence: representative time configs and a handful of logs per major system type.

By 60 days (Configuration convergence)

• Remediate the highest-risk systems first: identity, privileged access, perimeter, logging pipeline.
• Normalize timezone and parsing rules in the SIEM; document field mappings.
• Establish drift monitoring and a ticket-based remediation workflow.

By 90 days (Audit-ready operations)

• Run an end-to-end correlation test across multiple systems and retain the test evidence.
• Implement a recurring evidence cadence (aligned to your audit calendar) with clear artifact owners. ¹
• Add third-party timestamp validation to onboarding for critical SaaS and managed services that supply audit logs.

Frequently Asked Questions

Does AU-8 require NTP specifically?

AU-8 requires using internal system clocks to generate time stamps for audit records. ¹ NTP is a common way to keep internal clocks correct, but the key audit outcome is reliable timestamps in the records.

Are SIEM ingest timestamps enough to satisfy AU-8?

Usually no. You need event time generated by the system’s internal clock in the audit record itself. ¹ Keep ingest time as an extra field, not the primary one.

What’s the fastest way to prove compliance during an audit?

Bring (1) your time standard, (2) representative time sync configurations, and (3) sample audit logs showing timestamp fields and SIEM parsing. Map each artifact to an owner and collection cadence. ¹

How should we handle third-party systems that generate security logs (SaaS, managed services)?

Treat critical third parties as in-scope log sources and validate their timestamp format, timezone, and parsing during onboarding. Document the validation and keep sample logs as evidence.

What if isolated or legacy systems can’t sync to the enterprise time source?

Document an exception with compensating controls (local time source, increased monitoring, manual drift checks) and a plan to remediate. Keep the exception record and operating evidence so the assessor sees controlled risk.

How does Daydream help with AU-8?

Daydream is useful as the system of record for AU-8 ownership, procedures, and recurring evidence artifacts, so you can answer audits with the same package every cycle. ¹

Footnotes

1. NIST SP 800-53 Rev. 5 OSCAL JSON

2. NIST SP 800-53 Rev. 5