Alberto,
Sorry we missed this post. The Time is populated by the GPS signal. It is possible you started your flight prior to receiving a GPS Lock, thus the bad start date. Do you recall seeing a "No GPS Lock" or "Weak GPS Signal" at the start of your flight. This might have caused it to use the old system time as the time stamp. Also, has it done this again on other flights that you notice.
I have and idea that I will suggest or run by Walter and our dev team. Maybe if you use the completed time/date to log the flights, the would most like ensure that the unit has a GPS lock as you would have been flying with it. I'll also make a suggestion to list the PAst Flight from most recent to oldest, this would make it easier to get to the last flight and would make sense if it was logged from the completed time stamp. I hope this helps.