title: Application security: Counting days independent of system calendar
body: <p>I want to add a feature to my trial version of the application.  After first activation, I want to make it limited to 90 days.  But I am concerned about user's changing the date of system hence deceiving my application.
  Is there any possibility to make it fool proof in a way that even if user takes the calender back, application expires after 90 days of first activation?  First activation date has been saved in the database.</p>
  
  <p>Thank you very much.
  Furqan</p>