My timezone is Edmonton Mountain Standard Time, and is set automatically by Telus network. Last night, it switched to Eastern time zone. I use my cell phone for a 7 am wakeup alarm. It went off at 5 am MST because the Telus network misconfigured the time zone to Eastern Canada time zone. WTF? I woke up 2 HOURS EARLY because the Telus network BROKE????
I'm in Edmonton and haven't had any issues with my phone switching time zones. Either it's something very localized to your location or it's an issue with your phone. Has it only happened the one time?
I just set it back to "Automatic Time Zone - Use network provided time zone" to check and it works fine now. Before if I switched from manual back to auto, it would select EST. The strange thing is that if you looked at the time widget - it would show the EST time in big digits and underneath in small digits: "Home" with the correct time. As if I had travelled to a different time zone.