The attacks took place around 6 pm in Lybia, there is a 6 hour time difference, which would have placed Obama in Maryland around 1 pm est.
Obama was doing a photo op with soldiers at that time. http://potusnews.net/2012/09/potuss-schedule-for-911-anniversary/
http://www.communityforveteran.org/
Emails show White House was notified of terrorist attacks within 2 hours, and the emails specified “terrorist attacks”which would have been between 1-3 pm, Obama didn’t bother to meet with secretary of defense until after 5 pm.
http://www.whitehouse.gov/schedule/president/2012-09-11
The ambassador’s last meeting of the day was about 8 PM Libya time. The attack started anywhere from 9:30 to 10:45 depending on the source.