in clock settings, numbers go up by themselves

[Francesco]

Mint 16, Cinnamon, all updated.

To reproduce: click on clock. Click on "set date and time". Uncheck "use network time". Try to change the time.
That thing is haunted.

I have to put it one or two hours earlier, and be quick to ckeck "use network time" when it decides to reach the correct number. If I put the right one right away, before I can block it, it's already changed! Every time.

Today it reached midnight, then it olled over and got to the next date. Then also the date started going up by itself. A literal nightmare.