Shmacky-McNuts: Glad I could help. Linux change is better to change, but either gets the correct time. The clock is rather important over time, to prevent crashes and the like. If it is wrong, Windows becomes unstable.
I don't get it. I did as suggested, and it caused my clock on Linux to be wrong, as if now it wasn't taking the timezone into account or something, several hours wrong. Then when I reverted back from that and synced time with NTP, the time was correct again.
Also after I had applied that "fix", timedatectl returned some warning that the setting that I had just applied was negative and I should really consider changing it (I don't recall the exact warning and right now I am not on Linux).
So yeah, I reverted back from that setting, and yes indeedy, Windows time is always now several hours wrong when I boot to Windows after using Linux Mint on the same system. The workaround is to "Adjust date and time" => "Sync now" in Windows, then I get the correct time back, but I have to do that every time when I boot to Windows, if I've used Linux on the earlier boot. There would be no problem if Windows was sane and did that sync itself in every boot, but it doesn't seem to do that, have to do the sync manually... From the past I recall it would fix itself in Windows if you wait long enough, apparently when Windows finally decides to resync its internet time, but it sometimes feels it takes 10 minutes or so before that happens.
I have to look into those instructions again, it also occurred to me did the instructions expect that I am e.g. using a certain kind of NTP service, as in Linux I think there are several different options to choose from, like ntpd, timesyncd and chronyd. I presume ntpd is on its way out on newer Linuxes, on Ubuntu variants timesyncd is the most commonly used nowadays, and on RHEL-family chronyd. No idea about Arch, SUSE and such...