How to Fix Time Sync Errors in Windows 10 and Windows 11

A Windows clock that is only a few minutes off can cause far more problems than most people realize. It can prevent secure websites from loading correctly, interfere with Windows updates, cause sign-in issues with Microsoft accounts, and even create authentication failures on business networks.

Yet many people treat time synchronization errors as a minor annoyance. The reality is they shouldn’t. Your system clock is quietly tied to security, networking, software updates, and countless background processes — and when it drifts, things start breaking in ways that are surprisingly hard to trace back to the clock.

If you’re seeing messages such as “Time synchronization failed,” “Windows clock not syncing,” or your PC keeps showing the wrong time, this guide will walk you through the most effective fixes for Windows 10 and Windows 11. We’ll start with simple solutions and move into advanced troubleshooting when necessary.

• Understand why Windows time synchronization fails
• Learn how the Windows Time Service works
• Fix incorrect time settings and synchronization errors
• Force synchronization using Command Prompt and PowerShell
• Change unreliable NTP servers
• Troubleshoot firewall, VPN, and network issues
• Repair Windows components affecting synchronization
• Diagnose specific error messages
• Prevent future time sync problems

Why Time Sync Errors Happen in Windows

Windows relies on the Windows Time Service (W32Time) to keep your computer clock accurate. This service periodically contacts an internet time server using the Network Time Protocol (NTP) and adjusts your system clock when necessary.

When any part of that process breaks, synchronization errors can occur.

How Windows Time Synchronization Works

The process is simpler than many people think.

1. Your computer contacts a configured time server.
2. The Windows Time Service compares the server time with your local clock.
3. Windows calculates any difference.
4. The system clock is adjusted automatically.

If the service cannot reach the server or encounters a configuration issue, synchronization fails. What’s worth noting here is that some protocols aren’t forgiving about how far off your clock can be. Kerberos authentication — used by Active Directory domain logins — will refuse connections if the clock difference between your machine and the server exceeds five minutes. That means a clock that seems “only slightly wrong” can quietly lock users out of their own network.

Common Causes of Time Sync Errors

• Incorrect time zone settings
• Disabled Windows Time Service
• Unreachable NTP servers
• Firewall restrictions
• VPN or proxy interference
• Corrupted system files
• Domain synchronization conflicts
• Failing CMOS battery

Signs Your PC Is Not Syncing Properly

• The clock changes after every restart
• You repeatedly receive synchronization errors
• Windows Update fails unexpectedly
• Browser certificate warnings appear — even on websites you visit regularly and that rely on real-time data from external servers
• Microsoft account sign-ins fail
• VPN authentication issues occur

Quick Checks Before Trying Advanced Fixes

Before diving into command-line tools and service repairs, start with the basics. Many synchronization issues are resolved within minutes.

Verify Your Internet Connection

Time synchronization requires access to an online time server. Confirm that your internet connection is working normally and that websites load properly.

Check Date, Time, and Time Zone Settings

1. Open Settings.
2. Select Time & Language.
3. Choose Date & Time.
4. Enable Set time automatically.
5. Enable Set time zone automatically if appropriate.
6. Verify the selected time zone is correct.

An incorrect time zone often looks like a synchronization problem even when synchronization is functioning correctly. If these settings are already enabled but the clock is still wrong, try toggling them off, saving the change, then turning them back on. This forces Windows to reinitialize the synchronization process — and it resolves stuck states that simply leaving the setting enabled won’t fix.

Use the Sync Now Button

1. Open Settings.
2. Navigate to Time & Language > Date & Time.
3. Scroll to Additional settings.
4. Click Sync now.

If synchronization succeeds, the issue may have been temporary.

Restart Your Computer

Simple as it sounds, restarting Windows can resolve temporary service failures that interfere with time synchronization.

Restart the Windows Time Service

The Windows Time Service manages synchronization. If it becomes unresponsive, restarting it often fixes the problem immediately.

1. Press Windows + R.
2. Type services.msc and press Enter.
3. Locate Windows Time.
4. Right-click it.
5. Select Restart.
6. If the service is stopped, choose Start instead.

Set the Service to Start Automatically

1. Double-click Windows Time.
2. Set Startup Type to Automatic.
3. Click Apply.
4. Click OK.

This ensures synchronization services are available whenever Windows starts.

Force Time Sync Using Command Prompt

If Windows settings aren’t enough, Command Prompt offers more control.

Run a Manual Synchronization

Open Command Prompt as Administrator and run:

w32tm /resync

If successful, Windows will immediately attempt to synchronize with its configured time source.

Useful Time Synchronization Commands

Rebuild the Windows Time Service

If the service configuration is damaged, run these commands one at a time:

net stop w32time
w32tm /unregister
w32tm /register
net start w32time
w32tm /resync

This effectively rebuilds the service and often resolves persistent synchronization failures.

Force Synchronization Using PowerShell

PowerShell is particularly useful for advanced users and administrators.

Run PowerShell as Administrator and enter:

Restart-Service w32time

Then force synchronization:

w32tm /resync

To verify synchronization details:

w32tm /query /status

This allows you to confirm which server Windows is using and when the last synchronization occurred.

Change Your Internet Time Server

Sometimes the problem isn’t your computer. The configured time server may be overloaded, unreachable, or temporarily unavailable.

Recommended Time Servers

How to Change the Time Server

1. Open Control Panel.
2. Select Date and Time.
3. Open the Internet Time tab.
4. Click Change Settings.
5. Select a different server.
6. Click Update Now.

If synchronization suddenly starts working, the original server was likely the source of the issue.

Fix Firewall and Network Restrictions

Network Time Protocol uses UDP Port 123 for communication. If a firewall blocks this traffic, synchronization requests never reach the time server.

Check Firewall Rules

Review Windows Defender Firewall or any third-party firewall software to ensure UDP Port 123 is not blocked. This is especially important in corporate environments where strict network policies are common.

Check Router Restrictions

Some routers and network security appliances can block NTP traffic. If possible, test synchronization from another network to determine whether your current connection is responsible.

Disable VPNs and Proxy Servers Temporarily

VPNs and proxies occasionally interfere with synchronization traffic. Disconnect your VPN temporarily and attempt another synchronization. If the issue disappears, your VPN configuration may require adjustment. This is particularly common with business VPNs that route traffic through security gateways.

Repair Corrupted Windows Files

System file corruption can affect critical Windows services, including synchronization components.

Run System File Checker

Open Command Prompt as Administrator and run:

sfc /scannow

Allow the scan to complete fully.

Run DISM

If SFC identifies problems that cannot be repaired, run:

DISM /Online /Cleanup-Image /RestoreHealth

This command repairs Windows image files used by the operating system.

Troubleshooting Based on the Exact Error Message

Time Synchronization Failed

Usually caused by service issues, network restrictions, or unreachable NTP servers. Try restarting the Windows Time Service and changing the time server.

No Time Data Was Available

This typically indicates Windows cannot reach a valid time source. Verify internet access and switch to another server. If the problem persists after switching servers, you may need to manually reconfigure the time source. Run this command in an elevated Command Prompt:

w32tm /config /manualpeerlist:"time.windows.com,0x1" /syncfromflags:manual /reliable:yes /update

After running this, follow up with w32tm /resync to confirm the connection is restored.

The Service Has Not Been Started

The Windows Time Service is disabled or stopped. Restart the service and set it to Automatic.

The Computer Did Not Resync

Often caused by communication problems between Windows and the configured time source. Verify network access and review firewall settings.

Access Is Denied

This generally occurs when commands are executed without administrative privileges. Run Command Prompt or PowerShell as Administrator.

Advanced Fixes for Business and Domain-Joined Computers

Business networks often synchronize time through domain controllers rather than public NTP servers.

Why Accurate Time Matters in Active Directory

Active Directory uses Kerberos authentication, which is highly sensitive to time differences. Even a small clock discrepancy can cause authentication failures — and by default, any offset greater than five minutes between a client machine and the domain controller will cause Kerberos to reject the connection entirely.

Verify the Current Time Source

Run:

w32tm /query /source

Domain-joined computers should typically display a domain controller as the source.

Review Group Policy Settings

Administrators should verify that Windows Time Service policies and NTP client settings are configured correctly through Group Policy. Incorrect policies can override local synchronization settings.

Check for a Failing CMOS Battery

If your clock resets whenever the computer is powered off, the issue may be hardware-related. Unlike the continuously connected online time sources that physical and digital clocks rely on, your PC depends on a small coin-cell battery on the motherboard to keep the hardware clock ticking when the machine is unplugged. When that battery starts to fail, the clock loses its reference point between sessions — resetting the date, drifting wildly, or reverting to a factory default on every boot.

Common Signs of CMOS Battery Failure

• Incorrect time after shutdown
• BIOS settings repeatedly reset
• Date changes unexpectedly
• Synchronization problems return after every restart

Replacing the CMOS battery is usually inexpensive and can permanently resolve recurring clock drift issues.

How Incorrect Time Affects Windows Beyond the Clock

Many users don’t realize how many systems depend on accurate time. As covered in depth in why accurate time is critical for the internet, the consequences of a drifted clock extend well beyond what’s visible on your taskbar.

• Windows Update validation
• SSL and HTTPS certificates
• Microsoft account authentication
• VPN connections
• OneDrive synchronization
• Active Directory logins
• Security event logs

In business environments, inaccurate timestamps can also complicate auditing, troubleshooting, and compliance reporting.

Common Mistakes That Prevent Successful Synchronization

• Using unreliable time servers
• Selecting the wrong time zone
• Ignoring firewall restrictions
• Running commands without administrator privileges
• Disabling the Windows Time Service
• Overlooking VPN or proxy conflicts

A systematic approach is usually faster than trying random fixes.

How to Prevent Future Time Sync Problems

• Keep automatic time enabled
• Use reliable NTP servers
• Allow UDP Port 123 through firewalls
• Monitor Windows Time Service status
• Replace failing CMOS batteries promptly
• Review Group Policy settings in managed environments

Preventive maintenance is far easier than diagnosing synchronization failures after they start affecting updates, logins, and security services.

Frequently Asked Questions

Why does my Windows clock keep changing?

The most common causes are incorrect time zone settings, synchronization failures, or a failing CMOS battery.

How often does Windows synchronize time?

Windows periodically synchronizes with its configured time source. The exact interval varies depending on system configuration and network environment.

Can a VPN cause time sync errors?

Yes. Some VPNs restrict or reroute NTP traffic, preventing successful synchronization.

Which time server is best for Windows?

time.nist.gov, time.google.com, and pool.ntp.org are generally reliable choices when synchronization issues occur with the default server.

Can incorrect time affect Windows Update?

Yes. Incorrect system time can interfere with certificate validation and secure communications required by Windows Update.

Conclusion

Most Windows time synchronization problems can be traced to a handful of causes: incorrect settings, service failures, unreachable time servers, firewall restrictions, or hardware issues such as a failing CMOS battery.

The key is to troubleshoot methodically. Start with basic settings and synchronization options, then move to service repairs, command-line fixes, network diagnostics, and advanced configuration checks if necessary.

Accurate system time isn’t a convenience feature — it’s infrastructure. Everything from browser security to domain logins to software updates quietly depends on it. Fixing a sync error today might prevent a cascade of seemingly unrelated failures tomorrow, and that’s a trade-off worth taking seriously.