Today was the first time ever I used my backup to retrieve lost data. I wanted to upgrade my OwnCloud instance but instead I just removed the old one and installed a new one. After that I turned on Contacts on my mac and anticipated the OwnCloud to fill up with the data from it. But instead all data on my mac just dissapeared. I still do have the data on other devices but it was easier to use TimeMachine for the first time in real life.