My S3 has been displaying the wrong time lately; maybe 3 or 4 times in the last week.  It's not off by exactly an hour, so I know it's not a timezone or daylight-saving-time issue.  It's usually off by 15 to 25 minutes; just enough to make me late to work.

It's not only a 3rd-party app or widget issue; the actual phone time is wrong (in the upper, right-hand corner near the signal indicator).

Any ideas what would cause this.  I've searched around, and all I can find are forums w/ 6 pages of "Me too" responses.  A couple definitive answers/suggestions would be welcome.