You cannot be challenged if your status is set to 'away'.
The timezone is set to 'Eastern Standard Time' which will affect the time set in your calendars and emails.
Challenges expire after 7 days after which it is forfeited and the challenger wins the match.
The challenger cannot challenge more than 15 places above their position.
Max Simultaneous Challenges: Two up, three down
If you challenge and lose you will still gain a position.
You cannot challenge the same team/player twice in a row.