How do I pull the current time from a website?

I’m looking to pull the time from a website to see how long it’s been since a user last launched my application. Rather than reading the System’s time, which can be changed and exploited by the user, I’d like to read the time from an external website. Anyone have experience with that?

http://stackoverflow.com/questions/516788/getting-current-gmt-time

Maybe this can help you