In Germany, if you e.g. learned of an illness of a colleague, you are not allowed to disclose this to other colleagues or even the employee. I am wondering whether something similar applies to information regarding when they worked outside of usual office hours.
I work in IT and often on Sunday. The office building is almost always completely empty on the weekends. Last Sunday I found that for the first time I was not alone and another member of my team was there on call.
A few days later during small talk with other colleagues I wanted to mention that we spend the Sunday at the company together. Then I wondered whether this would be sensitive information protected under privacy laws.
I assume that it makes a difference whether he was on call (has to work, but could have worked from home) or whether he just felt like he wanted to finish some stuff on the weekend.
Please note that I am hesitant to mention that information not because working on the weekend is seen as illegal or against company policy. I am hesitant because I am giving away something that feels like personal information, i.e. what people do on their weekends which is usually free time. Someone might think: "Oh, this guy worked on the weekend? Interesting, he probably has no friends or does not want to spend time with his family.". Of course, on the other hand, the one who did come in on the weekend, voluntarily chose to come to the office instead of staying at home and therefore also volunteered that information.