This needs to apply restriction on changing datetime on the user from Group Policy. Hence you need to code for that. And depending on the system and user's permission I can't assure that it will work always.

Alternatively it is better to make your app so that it does not depend on system datetime while it is running. To do that you can read the system datetime at the start of your app. Then start a Timer and create your new datetime assigning it to the initial date plus timer instead of taking datetime from the system while your app running. Let me know if you want to do this process but do not know how to use timer.

Cheers