About a month ago, running Win-10, the clock in the toolbar started randomly losing time, jumping back by 5 or 10 minutes. I could sync it and it would keep perfect time, but then jump back. Then I upgraded to Win-11 and the clock started working perfectly for a couple weeks. Suddenly today it started again. I synced it this morning and it now reads 3:44 when the time is 4:19. The only thing that has happened is a new version of Mozilla was installed yesterday, Any idea what is going on? And how to fix it?
Could be the CMOS battery on your PC is dying.
Is “set time automatically” enabled?
Right click on the clock, and select Adjust date and time. That should bring you to a page that has a few time settings. One of them should be the “set time automatically” one. Make sure that is on.
If it was off, and you turn it on, then wait and see if the problem comes back. If it was already on, then try opening a terminal window and run the command w32tm /query /status That should tell you some information, including the last successful sync, and the source being used for network time.
Without an external time source, computer clocks are not very reliable.
Note that a virus, malware, or anything that generates a huge amount of ethernet traffic can slow down your PC clock.
If it’s not a dead/dying battery and your time is set to automatically sync, you might want to investigate a possible infection.
Set time automatically is enabled. When I opened a command prompt, the command w32tm/query/status got the message “The command /query/status is not recognized.” What is the CMOS battery? The computer is (almost) always plugged in so power should not be an issue. And it is not that the clock runs slow. It keeps time perfectly and then randomly jumps back by 5 or 10 minutes. I synced it 15 minutes ago and it has kept perfect time (to the second). Then will randomly jump back.
You need spaces in there, so w32tm /query /status The only point of that is to show if the automatic time sync is actually working.
If the system clock is too far away from the correct time, then automatic time sync won’t set it to the correct time. I don’t know what the distance is, but it could be 300 seconds or something relatively short. If the system clock gets far enough away from real time that it won’t sync, you can open an administrative terminal and run w32tm /resync which should force the time to update from the source.
If w32tm /resync gives an error, then we can go from there.
None of this explains why the computer loses chunks of time. One of the few things I can think of is that the time isn’t being reset properly when the computer wakes from sleep, but I really don’t know.
Have you checked to see if occasionally it approaches a black hole, or accelerates to a large fraction of c when you’re not looking?
What model is your laptop? The CMOS battery is a separate small coin battery used for timekeeping and to store some other system information. It typically has a lifespan of maybe 5-10 years, and one of the symptoms when it’s failing is that the clock can start to get wonky.
On some laptops it’s just a matter of unscrewing the bottom and putting in a new coin battery. On others it’s nigh impossible to do yourself and you have to take it to a specialist shop or use tools to melt down adhesives and such. It depends on your model.
Here is the result:
[c:\math\tac\my]w32tm /query /status
Leap Indicator: 3(not synchronized)
Stratum: 0 (unspecified)
Precision: -23 (119.209ns per tick)
Root Delay: 0.0538203s
Root Dispersion: 3671.9915856s
ReferenceId: 0x00000000 (unspecified)
Last Successful Sync Time: 9/25/2025 6:58:45 PM
Source: time.windows.com,0x9
Poll Interval: 10 (1024s)
The sync at 6:58:45 was forced by me. I don’t think it does it automatically. Besides it is the sudden jump backwards that causes it.
I may have something similar going on, as I noticed today when coming upstairs that the computer time was about 10 minutes earlier than on the stove and microwave. I went into the other room to check the time on the tablet and it was correct, and by the time I got back to the computer it was correct, too..
This is a desktop that’s always plugged in, but when idle it goes into sleep mode after a few hours. It’s possible that it loses time in sleep mode.
I think the CMOS battery is the most likely culprit — by a large margin. On older computers, they have to be replaced after a few years or your computer will lose time (among other issues). It’s not an “if”, but a “when”. Keeping accurate time is that chip & battery’s primary function, along with storing BIOS details. Losing accurate time is almost always caused by that, on older computers.
If you’re sure that doesn’t apply (i.e. it’s a very recent computer that doesn’t use a CMOS clock anymore or you just changed the battery)… then OK, it’s worth looking at time sync issues and such. But otherwise, a dying CMOS battery should be the first thing to check.
It’s not just running slow. It runs fine for a while and jumps back. Doesn’t sound like a weak battery to me. Anyway, I ran that w32tm again and got this result:
[c:\math\tac\my]w32tm /query /status
Leap Indicator: 0(no warning)
Stratum: 4 (secondary reference - syncd by (S)NTP)
Precision: -23 (119.209ns per tick)
Root Delay: 0.0550250s
Root Dispersion: 8.0007205s
ReferenceId: 0xA83DD74A (source IP: 168.61.215.74)
Last Successful Sync Time: 9/26/2025 9:11:18 AM
Source: time.windows.com,0x9
Poll Interval: 10 (1024s)
It synced this morning by itself when I turned it on and hasn’t jumped all day. I was in the middle of a zoom session last night when the computer suddenly turned off, screen went black. When I tried turning it back on it downloaded and updated the OS. Maybe it was something in software.
After reading these symptoms, I will be very surprised if the problem is not the CMOS battery. Windows has several sources for the time: the CMOS clock, the count of clock tick interrupts, and the remote time server(s). Of the three sources, the CMOS clock is the most likely one to be wonky, since unlike the others, it depends on a battery. What Windows does when one of the sources disagrees significantly from the others is likely to be complicated, and I don’t know the details of its algorithm, but I don’t think it’s safe to assume that it can’t be the CMOS battery just because the time exhibits discontinuous jumps. Also, the CMOS clock is not a mechanical clock, and a battery delivering a low voltage doesn’t necessarily just make it run slow.
The computer isn’t just using the CMOS clock. There are other timers (like in your CPU). What’s probably happening is that Windows is periodically detecting a significant enough time difference and re-syncing it for you. It doesn’t happen in realtime, but every X checks when it detects at least Y seconds (or more) or drift.
Anyway, this doesn’t have to be a hypothetical… if your laptop is user-serviceable, just open it and check (with a battery tester, or new batteries only cost a few dollars). Or if your motherboard supports it, you MIGHT be able to use the utility from hwinfo.com to check your CMOS battery voltage: https://superuser.com/a/1816407
Otherwise, you can leave your computer on with a running time drift log overnight:
w32tm /stripchart /computer:time.windows.com /period:60 /samples:480 /dataonly > timelog.txt
That will log the difference between your computer time and the Windows time server every minute for 8 hours (once per 60 seconds, 480 times) into a file called timelog.txt. You can check it in the morning to see how often the drift is occurring.