Find correct date and time, After user change in our own local machine?

Hai friends,



Now my team develop a small project. Before give original version to customer, we provide a Trial Version (only 15 days)



Calculate that 15 days from installation date and time. Suppose the user change own system date and time, it does not affect our day counting.



It means the user do anything, but after 15 days close the trial version.



How to do? any idea help me....Find correct date and time, After user change in our own local machine?
You don't.



No that guy's wrong, syncing up with the internet is a bad idea because not all clients will have an internet connection. Just let the flaw be.Find correct date and time, After user change in our own local machine?
Make (an encoded) registry entry that represents the date and time. There are websites out there (assuming the computers are wired) that will provide you with current date and time. Apply the same algorithm, and voila!



(Don't forget to set another flag, that once the trigger's tripped, it won't execute again)



Also, be sure you warn them the s/w will cease to function.



I suppose you could further put something in the contract, eh?