If every game has just had 24 hours added to it, and that's got 10 hours left, and your post was 9 hours ago, then it timed out 5 hours before you posted your message.
Is it possible that the game didn't have 24 hour, but showed 24hr due to not clicking refresh?
Another possibility is a game getting restored, I had a game restored and timed out when I was sure I had made all my moves! The game restored was restored with 2 hours on the clock and I returned to find I had timed out!
The server hasn't previously both (a) thought that a positive number was negative, and, (b) when adding 24 to a positive number, got a result less than 24.
So all the evidence points to one of your games not haing more than 24 hours on it, and instead having less than 0 hours on it.
And I don't think 'clicking refresh' should be the recommendation - this is an EWN game - it takes just as long to click 'refresh' as it does to make a move, so just make a move instead.
I think I've seen something similar. It seems like I've spent vacation days before my games hit 0 hours. Maybe when they hit 24 or 36 hours. I think I've lost several vacation days due to this.
@FatPhil It depends where you are on the site, if you have the list of games up then you would refresh, if in a game trying to make a move would show the correct time. It would make sense for a player to be relying on the game list in order to know they have no games with less than 24 hours!
Some sites autorefresh the game list every 3 minute so a player that uses another site with such a feature is understandably in danger of trusting the screen to provide uptodate info.