Does this thing run in UTC? I'm in the Europe/Copenhagen timezone (currently UTC+2) and the web app shows a time two hours behind localtime (and my pc is having the correct time from NTP).
I didn't know about the UTC thing in firefox, usually it will show the correct local time. But now that you mention it, the online booking system for the local vaccination centre shows the time in UTC, too. Recently I actually filed a bug report to their administration because of that.
All other sites I can think of — including https://time.is/ — are showing the correct localtime.