With the OS update 1.2.8 the behaviour of the “phone ownership” setting seems to have changed. I got my phone back from a repair and made a hard reset without mobile or WLAN connection. Now my ownership time is currently at 5 months 2 weeks. This dates back to some date in Ocober 2015. However, I received my phone only in January and I did the hard reset the day before yesterday.
So to me it looks like just the start date for the counter was changed from 1970-01-01 to something more recent. Or did anyone find an option to set the starting date manually?