title: Change system time for UNIX process?
body: <p>I need to test my C++ program, which uses system time.
  The program is large and it uses third party libraries which possibly also use system time.</p>
  
  <p>I want to see how my program behaves for different dates / times.</p>
  
  <p>Is it possible to change the system time only for one running process in UNIX?</p>
  
  <p>Many thanks...</p>