Get date from server?

Here comes a .NET question:

I need to save in a database the current date when the player registered, or something else.

But I want to record the “real” date, not the user machine’s date, as he could easily change this date.

So I need to record the date from a reference outside the user’s machine, maybe from a server, how could I do this?

(The function System.DateTime.Now gives me the client machine’s date)

I thought I could create a PHP script that gets the current date from the server, then I could read the date from that page. Is there something wrong with this method? Are there any alternatives?

Here is the answer I use to keep my time accurate across all devices by utilizing the internet/server time :