If I am reading the "stereo instructions" of the court system correctly, DC has up to 90 days to appeal to the Supreme Court. So roughly 12/27/17.
90 days from entry of final judgment, which would be the denial of en banc. Relevant section of Supreme Court Rule 13.1:
"Unless otherwise provided by law, a petition for a writ of certiorari to review a judgment in any case, civil or criminal, entered by a state court of last resort or a United States court of appeals (including the United States Court of Appeals for the Armed Forces) is timely when it is filed with the Clerk of this Court within 90 days after entry of the judgment."
Extensions are governed by Supreme Court Rule 13.5:
"For good cause, a Justice may extend the time to file a petition for awrit of certiorari for a period not exceeding 60 days. An application to extend the time to file shall set out the basis for jurisdiction in this Court, identify the judgment sought to be reviewed, include a copy of the opinion and any order respecting rehearing, and set out specific reasons why an extension of time is justified. The application must be filed with the Clerk at least 10 days before the date the petition is due, except in extraordinary circumstance."
The Supreme Court has a very liberal definition of "good cause." "I'm an overworked government lawyer" is "good cause."