>How can you find out current date from the web (not using DATE() function)

Usually, you have your computer set to obtain accurate time from a time (NTP) server on the Internet. With Windows OSs this is time.windows.com by default. As long as your local machine can periodically attach to this server to update its time, its reported time will be quite accurate, so you can use VFP DATE() and related functions.

Are you concerned that users may manually change the date/time of a given computer? If so, I believe Group Policy can be used to prevent that from happening i.e. deny users permission to change date/time.