@nordax since you do not know what and how it was fixed, this could be a bad sign. you should really inquire about what was repaired. Check to make sure that you have power from your AC adapter and that your battery has power. The difference in date could be because it was disconnected from power and never reset. It does not sounds like a CMOS issue since that date would be more than a day behind.
Download the service manual [http://content.etilize.com/user-manual/1019383350.pdf|from here] and check your power adapter connector