MySQL time settings

I have been quietly running OpenHAB2 for a few years now, lately without paying too much attention due to other stuff coming up.
I can faintly remember that sometime this spring, I had to add
to my jdbc mysql URL, because something didn’t work anymore (or so does the git log of my /etc/ folder say and I think I remember).
Now, since I do not live in UTC zone and my server is set to Europe/Berlin, my charts started to look weird (shifted to the future with a horizontal line of about an hour), although that seems to have been the only effect. In particular timestamps in DB are still fine and match my local time.
No with a new project, this started to bother me and I changed it to

Now my charts look normal again, but GMT+2 is summer time here so it seems like it will be wrong again in one week.

How do I deal with this properly?

Did you already install a ntp client on OS-side?

Yes (on both side, what ever OS means here), but I absolutely don’t see how that is relevant. My system time is fine. This is purely about the the database connection and as far as I can see for now, it only manifests in chart display.

OS is Operating System.
The point is, that if timestamps are different, a common problem is that system clocks are not synchronized.

What version of openHAB is involved here? (Since there was mention of a couple of years)

Are you using OH persistence service to store data? (It’s not spelled out)

I have done my software updates, so I am at 2.4, but I have not done any major configuration updates. For that reason I am e.g. still at mqtt1.

I am using the persistance service, and the line above hat to be modified in the mysql.cfg for the connection to my MariaDB.