how to get real date (not system date) by c# or c++?

Question

Is it possible to get real date (not system date) without any connection to internet? I developed my application by C#. DateTime.Now gets system date but I want to know real

Answer 1

No. In the absence of any external communications, all you've got is the clock in the computer. If you're not going to trust that, you're stuffed.

Of course, if you're trying to prevent someone from blowing a timed trial licence of software, you could do things like recording the latest UTC time you've ever seen, and becoming suspicious if you see an earlier startup time than the previous startup... especially if you see that repeatedly. That's not the same as getting the real date, of course.