Hi Piotr,
as you do not seem to use the high resolution timestamps (which can theoretically produce time shifts, although not to this extent), I'm pretty sure this is caused by time synchronization on the machine that produced the log.
If you are not using high resolution timestamps, SmartInspect just calls a function to get the local time (Now() in case of the SmartInspect Delphi library) and writes/sends that directly to the log file or Console.
If the machine loses a few minutes per day (a common issue with computer clocks) and the machine is set to synchronize its time with an outside server (I believe this is automatically the case for Windows machines that are members of an Active Directory), this might explain the time shifts.
Regards,
Tobias