I have the same issue. I have players in France, London, New York, SF, and Brazil.
How can I make it so users can change it to 15 minutes before match -- someone in London tried making a change but they couldn't because of the timezone issue.
"I’m in the London office and we found a bug. It takes the time from our computers so it thinks Germany-Portugal (scheduled to play at 9am sf time) has already played, because it is after 9am here.
My colleague tried to change his prediction and was prevented due to this. He emailed me his change so I can give to you!"
Thank you in advance!