Hi all,
first I'm gonna comment only technical stuff, as other is going off direction to nowhere

I believe it is not possible that you get corrupt files on hard drive just because the date is not correct on your Q10. Don't get me wrong I do not say that your files are not corrupt I only say it is not possible because of wrong date. Yes, you can get into some weird stuff which are consequence of wrong modify date of file in the file system - but the result is never corrupted file. The things that might be affected include restoring files from backup (or syncing them between different locations) when files comparison is made on file's modify date data - which usually is. In short, the cause for corrupted files should be searched elsewhere.
Now also some small/humble/personal/non technical comment:
I understand your frustration, I would also personally also like to see the date to be retained between shutdowns and I would also understand to loose date only when you unplug it from AC power. But I also believe that there are many other things that are much worse than Q10's date issue.
About statement that manufacturer should state clearly that box needs internet? Maybe you're right, but then again how many manufacturers do put in theirs adds that retaining date requires battery? Even this is technical fact, I haven't seen one so far - are they also misleading customers? Believe me, 70% of TV commercials is more misleading than Q10's advertisement. Should they all be sued? Here I'm with you, yes they should

So what are your options:
1. Set your date manually and leave your box always turned on
2. Set you date manually each time you turn it on