python time since epoch hacking system variable

I am trying to figure out whether it’s safe to let a payed software check its own license date validity using the client’s computer

the way this is done is by invoking time.time() function from python and comparing it to the hashed license expiry date. if the time.time() returns anything after the expiry date than the software throws a license expired error.

The concern I have is whether it’s possible for someone to change some system variables and get time.time() function return a different difference since epoch than the real actual one.

thanks

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Alternatives to CCBill or Epoch