Testing with timezone Etc/GMT, and changing the offset starting at -0 and moving right-to-left by an hour, so GMT-1, GMT-2, etc (and this timezone doesn't have daylight changing considerations).
The widget starts showing the wrong days at GMT-5.
The times shown were correct and localized to the offset (limited to the scope of testing written above).
If you view with GMT-12 (maybe you happen to hale from Baker Island and had time traveled so that you're currently observing standard time ) then the first talk finally is happening on Thursday, 11:00 PM, so I could see an argument being made for showing Thursday as the first day.
My schedule is rather full at the moment. I'd like to dig in further and fix this before next week (being the start of the conference and all), but I put the odds of finding the time to do so around 10%.