Creating the unbreakable 15 day's trial.

I just wonder if is there any method to get the program last for 15 day's only.

I watched like 10 examples but all of them can be "cracked" by simply moving your date/time at computer backward 15 day's, or simply reinstalling application.

Later on i will use MySql database on host to create product activation form. For now i just need to make my program unusable after 15 day's

Thank's
Anel