How does Hulu know my local time when I am behind a VPN?

To see what would happen, I attempted to access Hulu from a VPN outside the US. As I expected, Hulu detected the VPN. My understanding is that this is because Hulu is aware of the IP address ranges that belong to known VPNs. However, what caught me by surprise was Hulu’s ability to display the time of the incident in my local time zone. How can this be possible? How does Hulu know in which time zone I am actually located?