Help with time server

Hi all I’m running ubuntu mate on my raspberry pi3 its running great but I have a small issue with the time and date my internet runs off a captive portal network and login is required to be able to update the time does anyone know what web address it uses to get the time from the internet so I can get them to maybe add the address as a free site. Then it should update the time and date without having to login every time.


does this help?: