The VM clock says 10:42 while your watch says 10:57, and it is worse every week. Files get strange timestamps, schedules fire late, and one day a domain login refuses outright because the clock is too far from the server's. Virtual clocks drift by nature - the fix is understanding which tool should be correcting them, and letting only that one do it.
A physical PC has a hardware clock chip. A VM has a simulated one, and simulation loses time whenever the host is busy, the VM is suspended, or a snapshot is restored. Two separate systems try to correct it - VMware Tools time sync to the host, and the guest's own Windows Time service to a server or domain. When both fight, the clock flaps. When neither runs, it wanders. The whole fix is choosing one master and setting it up properly.
The guest counts time by tracking timer interrupts, and under load some get delayed or merged. Suspend the VM and its clock effectively sleeps too. Restore a snapshot and the guest wakes believing it is still the snapshot's moment. None of this is damage - it is the physics of a simulated clock on a shared machine, and it is exactly why Tools carries a time sync feature in the first place.
With Tools running, the guest clock is pulled to the host's clock at power on, at resume from suspend, and periodically when sync is enabled. Two honest details matter. First, this makes the host's clock the master - a wrong host clock makes every guest wrong together. Second, Tools' periodic sync historically corrects a clock that is behind; a guest running ahead may need a reboot or a manual correction rather than waiting for sync to pull it back.
Decide who owns the VM's time and disable the other candidate:
Check what Windows Time is doing inside the guest with w32tm /query /status - it names the source the guest is actually trusting.
The dramatic cases - a VM waking hours or days in the past - come from long suspends and snapshot restores. Tools sync at resume repairs ordinary cases automatically. If a guest wakes with a clock that is still badly wrong, a full guest reboot forces a clean sync at power on. Build the habit too: a VM you intend to keep should be shut down or left running, not suspended for a fortnight and expected to know what day it is.
Before blaming any guest, look at the host. If the host's own clock is wrong or drifting - a dying CMOS battery on an older desktop does exactly this - every guest syncing to it inherits the error perfectly. Enable internet time sync on the host, confirm it agrees with your phone, and only then judge the guests. It is the cheapest step on this page and the one most often skipped.
The video covers the Tools and configuration habits that keep VMs quietly healthy - time sync included. Watch it and audit your own VMs.
Watch Full VideoBecause a domain-joined guest does not take time from your host - it takes it from the domain hierarchy. If the domain controller's time is wrong, every member follows it faithfully. Fix the time at the domain source, and leave Tools periodic sync off on members so nothing competes with it.
Either works; both together do not. open-vm-tools can sync to the host, or chrony can sync to NTP servers like a physical machine. Pick the one that matches how the rest of your systems are run, and disable the other cleanly.
It breaks real things. Domain logins fail beyond roughly five minutes of difference, certificates can appear expired or not yet valid, scheduled tasks fire at wrong times, and log files become unreliable evidence. Treat a drifting VM clock as a fault, not a quirk.