I saw on YouTube this morning that the livestream start was different from the game jam start (on itch) by an hour and 15 minutes. I get it would be offset (people need the theme to get started).

Any help would be greatly appreciated. I missed the start last time and I don’t want to be late again! 

another thing would be what time is the theme revealed in the stream? I’m trying to make some plans for the morning but be back in time for the jam.

The time on Itch is when the jam is starting.  On my end it looks like the livestream is starting 15 minutes before the jam (for PST, livestream starts 8:45 AM and jam starts 9 AM which is the time shown on the Itch page), maybe another host updated the time to be correct in the time? You may want to check again and see if the time is correct now. The theme is revealed at the end of the livestream so a few minutes before the jam.