Many frequent flyers stand by the fact that if you keep yourself hydrated and get plenty of rest the effects of jet lag should go within a few days. However, there are some other ways to stop Jet Lags effects and there are remedies to stop you getting it all together.
Kos to Krakow jet lag information
Lets assume you left Kos at 9:00am. The flight takes approximately 2 hours 31 minutes so you would arrive in Krakow at 9:12am Kos time which is in fact 9:12am Krakow time.
Your body will be telling you that its 9:12am but actually its now 9:12am