This afternoon I switched the box on from stand-by. I noticed that the time was wrong, it was set 1 hour ahead. The timezone was still set correctly. Changing channels didn't help. After a reboot this problem was cured but then I noticed another weird thing: most of my timers were showing a starting time of October 2016 instead of February 2016. I tried editing them via the Webif but that didn't work.
Any ideas what could have caused this? The only thing apart from the usual was copying 500 GB from an external hdd onto the internal disk but I fail to see a connection there.
I recall that once before my timers were messed up similarly and I still don't know what went wrong then or now.