I have no idea about B&N (I can't go direct to them because I'm in the UK), but for Kobo, you have to have everything done (uploaded, prices set, etc) by midnight on 18th December.
You can set a release date in the future, if you wish, so you could set it to release on 24th December.
Full details here:
http://kobowritinglife.com/2013/12/1...rver-schedule/