The TimeSync page notes:
Using Boot Clock Randomization, i.e. after boot, the clock is set randomly between 0 and 180 seconds into the past or future. This is useful to enforce the design goal, that the host clock and VM clock should always slightly differ. It is also useful to obfuscate the clock when sdwdate itself is running, because naturally at this time, sdwdate hasn't finished. sdwdate runs after booting.
By randomly moving the system clock a few seconds (and nanseconds) in the past or future during boot, this enforces the design goal of a slightly different host clock and any VMs clock, even before secure timesync has succeeded. This prevents time-based fingerprinting and linkability issues, thereby improving security and privacy. 
/var/log/bootclockrandomization.log in a text editor of your choice as a regular, non-root user.
If you are using a graphical environment, run.
If you are using a terminal, run.
Run the following command. Note:
- Qubes-Whonix: Use a StandaloneVM or a separate Template.
- Non-Qubes-Whonix: No extra steps are required.
Boot Clock Randomization will no longer occur after reboot.
- Notably, one recent change is the 0-5 second time window is no longer excluded in the process, as it was found to aid fingerprinting.