Yes, blame me for this one. I didn't have things ready quickly enough to fix certain important user experience aspects like "showing the timezone".... which is kind of a basic and critical need.
Anyways, the widget at https://2020.nixcon.org/#program localizes to your timezone (but also shows weird dates sometimes).
Times from the cfp subdomain are all in UTC.
https://cfp.nixcon.org/nixcon2020/schedule/