Is there a method to auto-schedule Do Not Disturb?
While I do not use the feature, ObiPLUS (even the "free" version) provides basic time based incoming call routing. Unfortunately, while a OBi1xxx can be a client, as far as I know it cannot be a master (not sure if there was ever a plan to allow that). That means other than the light timer (obligatory xkcd ref:
http://www.xkcd.com/1495/ ), or the equivalent of unplugging the phone (I know of people that have unplugged their phone every night for decades to avoid interrupting their sleep; it was as automatic as brushing their teeth), you would need to consider either an additional devlce (Obi202, asterisk server, etc.) or an upstream provider that supports your needs.