Saturday. Playing Eastern on a Friday night (in my timezone) and coming up with decks on the day of the tournament is a fun way to unwind after a week of school :>
(It would be nice if we could have 3 official tournaments a week, but it would put a strain on the TO team, not to mention that SG might shoot it down like the idea of a third League each season -- due to award spamming, not enough prize codes, etc.)