I have a Sony xperia c6 ultra. I’m tring to set my timezone (and date/time) to automatic (via GPS and network).

I can change all this setting and can see the clock on top changing too. but when I left the config screen the time zone come back to China and the clock turn back again to the old time.

When setting all by hand and disabling all automatic settings, I can set the time/date and time zone but again, when left the config screen the time zone come back to China and the time/date still the one I set.

Having the date/time to my country and the time zone to China and disabling all automatic updates I can’t use some app like Whatsapp.

Smell like a custom ROM joking me or a virus… If it is not the original ROM can someone point me to instructions how to put my phone back to original ?

More info:

Sony Xperia C6 Ultra Android 6.0  Kernel 3.4.5-526212 se.infra@SEI-44#1  Build number 23.0.1.A.5.77 Custom Build version ALPS.L1.MP6.V2_GXQ6580.WEG.L_P69