I just found this off their website:
The online submission or postmark deadline for Early Action applications is Sunday, November 1st. We strongly encourage you to apply online. Online submission will be possible at
www.commonapp.org through the end of the day on Sunday.
If you are applying on paper and your local post office will be closed on Sunday, we encourage you to mail your application on Saturday, October 31. If this will be impossible, please mail your application early on Monday, so that it will be postmarked no later than November 2nd.
so, i think we have all day sunday. Can anyone confirm this to make sure i'm just not having a massive mis-comprehension?