I've been having the same problem where my Samsung Galaxy Centura will suddenly lurch back 5, 6 or more hours in time.
And yes, some of the tricks like going into the system settings menu and unselecting the automatic time and date things works fine to correct it, but that still makes this cell phone worthless and unreliable for an alarm clock. And it makes it an inconvenient replacement for a wristwatch.
The clocksync app does not work on my phone. I had high hopes for it, but it does not work for me.
And reading some of the posts here where people only paid $29 for their Centuras lets me know I got really ripped off. I bought mine at Radio Shack and they charged me $114. I wish I had known they were so much cheaper elsewhere. If I had only paid $29 for the phone, I would figure, eh, who cares about the time issue? But at $114 I'm mad about it.
I know this, I will saving up money for the next phone I buy, and this next time around it will be the latest version of the iphone. I'm done with androids.
Until then, I am stuck with two cell phones. The old Nokia 1100 that I bought way back in 2004 on Net10, with the old fashioned grey liquid crystal display. That phone is nearly indestructible and it is the one I use for my alarm clock and wristwatch replacement, and for most of my phone calls because I am new to smartphones and I just don't like dialing on the new touch screens. It's just not as easy for me to use as the old fashioned kind of cell phone.
And of course, I have the Centura for surfing the web at wifi locations. It is on Tracfone. I figure I am just starting out, getting used to smartphones and getting my feet in the water for the first time with them. In a few months, maybe more, once I get more used to using them for phone calls, etc., I will make the jump to an iphone.