OEL 6.3 - System time changes after login, moves back by a day or so. But location remains same, just checked.
Have to manually edit the time each time. Does not happen during immediate system restarts. This time error shows up specially after login after a day or so.
NTP sets the time when the service restarts. Since the OP outlined that it does not happen during a system restart I would not think it is a problem of NTP. NTP can also not be used to bypass the ill effects of a dying or bad CMOS battery.