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Thnx Bagshot! thnx spcan! my app is offline i cant used server or internet time
And is there any possibilities to my app nothing related to system date? somehow set the time on database or any method?
I think it might be work on my case big thnx #sneeze.
I don't know if this can help or not but here is it 😃 https://code.sololearn.com/cd6hB5y36wJg/?ref=app
You could design an api that retrieves the correct date and time, and get your app to call the api as it starts up. WCF is one way of doing this, but you will need a server to host the api. Other than that, I'm not really sure of any other way that can't be easily hacked by users.
Require internet connection to start the app. Then lookup the atomic time on an internet service (many pages do, even google i think) With this, the user cannot cheat the expire date.
Save the date everytime when the program starts. Before you save this date check if the system date is more recent than the saved date. If this is not the case then it us not valid and some one changed it.
You could work with a number, that is hided in the database. But you need some sort of tick system to define time, it does not necessarily mean seconds though. So than the user get x number of ticks and this number is lower every time a tick expires. Or may do not use tick but button-click. Than a user can use the app for x button-click and after that it does not work anymore. If you make the number high enough the app should work for a reasonable amount of time.