I'm creating an application that needs to keep track of the number of days that have passed. For example, once 30 days have passed since the first time the app was opened, display a message.
This has been done a zillion times I'm sure... "Your evaluation period will come to and end in 10 days" comes to mind. So is there a standard approach for such a thing? Something that deals with the user changing the system time/date?
My app is is in Qt if that matters. So I don't have access to OS calls. I'm just wondering if there's some typical approach before I invent my own.