Time server settings are saved in /etc/ntp.conf
so open your favorite editor and make this simple change.
sudo vi /etc/ntp.conf
The relevant section looks something like this (It may say ubuntu instead of debian, but it is the same problem either way):

So all you need to do is change it to look like this on all the relevant computers:

then reboot them.
Voila, the systems are now all using the NIST/NBS Master Clock to synchronize. Stratum 1 is the primary source, and Stratum-2 are a single hop away from it.
The pools are anywhere from 12-16, just like Windows when it uses pools.
You can verify that it is working at Level 1 by using this command:
ntpq -p
Which gave me this output:

FileZilla is now running unbelievably faster as it is able to skip more files!
Amazing difference. Time synchronization is an excellent experience.
This is the best that can be attained via the Internet.
time.nist.gov
is a load balancer that will find the best server for any particular location.
If you want your system to announce the time to you on the hour, you can use this procedure:
16.04 LTS How to make the system announce the time at the top of the hour with eSpeak
In Windows this same change is even easier. Just click on the clock and follow the prompts to change the Internet time to time.nist.gov then update.
By doing that, even transfers into and out of Windows (for hard drive backups) are a LOT faster as it skips files with the same creation date on both sides.
This has a pleasant side-effect of minimizing the amount of time it takes to ROBOCOPY out to a backup drive, too.
If you want Windows to announce the time to you at the top of the hour, use this procedure:
https://superuser.com/questions/1268702/how-to-make-windows-speak-the-time-at-the-top-of-the-hour
Once all the systems are set to this time source you can hear them announce the time all at the same time.