Have you set it up to autmatically adjust time?

 

You must be joking...it's the first option right at the top of the screen in the "Date and Time" settings.

 

Oh wait, you must have a WiFi model which does't have the Automatic setting since there is no cellular network to sync with over the air (3G model has this setting).

I don't know why it would just randomly change the time settings and this is the first I've heard of this. Perhaps you have a rogue app that is messing with the system?

There is a time sync app in the Market, but you need to root the Tab for it to update automatically. It's called ClockSync. It doesn't update automatically if you don't have root access though.

 

Have you verified the time zone set on your Google account?

 

Did you try rooting and ClockSync?

 

I googled for time bugs or issues with the Tab and couldn't get any results, which tends to indicate that it's an uncommon issue.

Have you tried a factory reset to wipe the Tab clean and start fresh? It means you need to reinstall your apps and put music, videos, whatever back on it, but it starts it off like a new tablet again.

 

Doing a factory reset is a bit of a hassle, but it wipes everything off the tablet and resets the firmware which may be "glitchy" (a highly technical term).

If you sync your contacts, calendar, etc. through Google, they will resync again automagically, so no issue there. You simply need to install any apps you want again, and transfer over songs, videos, etc. If the reset fixes the time bug, then I think the hassle of the reset is well worth it.

For perspective, every time I do a firmware update on my phone or tablet, I do a factory reset before the update, and after. This gives me a clean setup of the new firmware, and I've never had issues that others have complained about when simply updating and no doing a reset. Either I'm lucky, or the reset does a better job with the firmware setup. I consider it to be like wiping my PC and doing a clean install of Windows whenever a major change is made.

So for my Tab, I've only reset it once to update to v3.2, and my phone I've reset twice to update to v2.3.6. No big deal to me and I'm "glitchy" free.

 

I was having this problem too. After about 5 times though, it finally kept what I set the time to.