This may help, when setting up an alt in different time zones, great way to start is GMT so North America eastern time right now it GMT -4 Central is -5 so 10pm eastern time right now is 2am GMT which is clearly not within the 15hours spread.
So 9am - 12am GMT = 5am - 8pm eastern time
I also find if I get both teams to declare when they are available days and times, then convert it to my time zone, it's a lot easier to see when a game can be played and suggest that time and day.
The answer to when are you available to play cannot be when I'm green. List the days and times between both team members, then decide who will be setting for each team and have them work it out. If you know when your partner is available then you don't need to check with them, just decide between the 2 setters for the game.
You can find out what your current GMT is by asking the question to google...
We will also have time zones change over the next bunch of weeks because of summertime daylight hours... so check as you set.
Cheers,
Really hope this helps a bit