How to make a trial version of our software

Question

I try to make a trial version of our software. But I am not able do it properly. When the clock in my system is changed, it is not working.

SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
Calendar expiredate = Calendar.getInstance();

try {
    Date date = sdf.parse("24/06/2015");
    expiredate.setTime(date);
    if (Calendar.getInstance().after(expiredate)) {
        JOptionPane.showMessageDialog(null, "Sorry your software has expired", "Expire",
            JOptionPane.INFORMATION_MESSAGE);
        System.exit(0);
    }
 } catch(ParseException e) {
    // ...
 }

Answer 1

You have to decide how much energy you want to spend. If your application only runs on the client's system (meaning: it doesn't need a connection to a central server) ... then your options are pretty much limited.

Of course, your application can save date/timestamps ... but that won't help when people start tampering with the system clock.

Long story short: you should balance between "easy to implement; but probably easy to circumvent" and "hard to implement; and thus probably easy to do get it wrong". In other words: keep in mind that such "licence checking features" could make it too hard for your potential customers to use the software. Or "worse": you spend a lot of time for some "great security solution" to this problem, and while implementing it, you add various bugs into your software. Don't underestimate the efforts that will be required to pull up a solution that can't be cracked by a motivated user ...

Final suggestion; try a different approach: focus on creating a great user experience with your application (but maybe with restricted feature set). Just convince your customers that your application is worth paying money for; and don't provide "trial licences"; but a free "trial version" with less functionality than the real product.

Answer 2

$sql ='SELECT * FROM finsys.user WHERE username= "$user" AND password = "$pass" AND now() <= "20-Dec" ';

if yes, delete user record from database..

the customer does not change the system date change for a time-pass. if they show the trial over message then they may change the system date.

Do not provide any trial over message.. provide message as 'user authentication fail'.. They won't be able to know why this happened; before that DB will change..