Quick fix: Open Settings → Time & language → Date & time, toggle Set time automatically Off and back On, then click Sync now. If “Sync failed”, the Windows Time service is stopped — restart it with net stop w32time && net start w32time from Terminal (Admin).

Your PC clock drifts by minutes per day, or your scheduled tasks run at wrong times, or Outlook shows weird timestamps. Windows is supposed to sync the clock with time.windows.com automatically, but the Windows Time service can stop or get misconfigured. Three things to check: service running, server reachable, time-zone correct.

Symptom: System clock drifts; “Sync now” shows “Time synchronization failed” or “The time service is not running.”
Affects: Windows 11 (and Windows 10).
Fix time: ~10 minutes.

What causes this

The Windows Time service (W32Time) is responsible for clock synchronization. It runs in two modes: NTP client on workgroup PCs (syncing to internet time servers) and domain time hierarchy on Active Directory-joined PCs (syncing to the domain controller). The service can be stopped, disabled, or misconfigured by Group Policy, antivirus software, or a partial Windows install.

Other common causes: outbound UDP port 123 blocked by firewall, a default time server unreachable due to corporate proxy, or a CMOS battery failure causing time to reset at every boot.

Method 1: Reset and restart the Windows Time service

The standard fix for “service not running.”

Open Terminal (Admin): right-click Start → Terminal (Admin).
Check the service’s state:
```
Get-Service W32Time | Format-List Name, Status, StartType
```
Status should be Running, StartType should be Automatic.
If stopped: start it:
```
net start w32time
```

If StartType is Disabled or Manual: set to Automatic:

Set-Service -Name W32Time -StartupType Automatic
Start-Service W32Time

Force a sync:
```
w32tm /resync
```
Output should say The command completed successfully. If it says “An error occurred” with code 0x80072AF0 or 0x80072F76, the time server is unreachable — see Method 2.
Check the configuration:
```
w32tm /query /configuration
w32tm /query /status
```
Status output shows last sync time and offset.

This handles 60% of clock-sync issues — service stopped or misconfigured to manual.

Method 2: Change to a different time server

For when the default Windows time server is unreachable (firewall, corporate proxy, etc.).

Open Settings → Time & language → Date & time.
Scroll to Synchronize your clock. The dropdown shows the current server (default: time.windows.com).
Try a different server: pool.ntp.org, time.google.com, or time.nist.gov. Pick from the dropdown if listed, otherwise see step 5 for custom.
Click Sync now. Wait 10–30 seconds. Status should change to Last successful time synchronization with the current date.
For a custom server not in the dropdown: open Terminal (Admin) and run:
```
w32tm /config /update /manualpeerlist:"pool.ntp.org,0x9" /syncfromflags:manual /reliable:yes
w32tm /resync /force
```
The ,0x9 suffix means “use symmetric active mode and special poll interval.”
Verify: w32tm /query /source. Should now show the new server name.
If still failing: open Windows Firewall → Allow an app through firewall. Verify Windows Time is allowed.

This route handles corporate networks or ISPs blocking the default server.

Method 3: Fix CMOS clock and resync

For when the clock resets to a far-past date every boot.

If the clock shows a date from 2009 or similar after every reboot: the CMOS (BIOS) battery is dead.
Confirm by opening BIOS/UEFI (press F2/Del during boot). Look at the date/time display in BIOS. If it’s also wrong, BIOS isn’t keeping time — battery is dead.
For desktops: replace the CR2032 coin-cell battery on the motherboard. Costs $1–2 at any electronics store.
For laptops: the CMOS battery is usually soldered or part of a small auxiliary battery pack. May require professional service.
After battery replacement, boot into BIOS, set correct date/time, save and exit. Boot Windows.
Then in Windows: Settings → Time & language → Date & time → Sync now to fine-tune from NTP.
If you can’t replace the battery immediately: configure W32Time to sync more aggressively. Run:
```
w32tm /config /manualpeerlist:"pool.ntp.org,0x1" /update
sc triggerinfo w32time start/networkon
```
This makes Windows sync immediately on network connect, so the clock self-corrects within seconds of boot.

This is the hardware-side cause that many forum threads miss. If your clock resets to the same wrong date repeatedly, software fixes won’t help.

How to verify the fix worked

Run w32tm /query /status. Output shows Source as your chosen NTP server and Last Successful Sync Time within the last hour.
Check time precision: w32tm /stripchart /computer:time.windows.com /samples:5 /dataonly. Output shows the drift in milliseconds — should be under 100ms.
Reboot. After login, check Settings → Date & time. Last sync should still be recent, not several days ago.

If none of these work

If sync still fails, the firewall is blocking outbound NTP (UDP port 123). Open Windows Defender Firewall with Advanced Security (wf.msc). Outbound Rules: look for any rules blocking UDP 123; if present, disable. For corporate networks where NTP is genuinely blocked, ask IT for the internal NTP server address — often something like ntp.<company>.local — and use Method 2 with that server name. For Windows Time service that won’t start with cryptic errors: re-register it. Open Terminal (Admin) and run w32tm /unregister, then w32tm /register, then start the service again. This rebuilds the service’s configuration in the registry from scratch. For PCs that recently had a CMOS reset (after BIOS update or motherboard work): you may need to set the date in BIOS once, then Windows’s NTP sync takes over.

Bottom line: Check W32Time service is running and configured. Switch to a different NTP server if the default is blocked. Replace the CMOS battery if the clock resets every boot.