'American Idol' Finalist C.J. Harris Gets a Month in Jail

"American Idol" finalist Curtis "C.J." Harris is back behind bars -- and will be for the next month -- all because he claims he mixed up his dates.

Law enforcement officials in Alabama tell TMZ ... Harris turned himself in Monday after an arrest warrant was issued due to his skipping out on a court date last month.

Harris was supposed to be in court Oct. 27 for his drug arrest, but we're told he claims he confused that for another date. We broke the story ... Harris was arrested in an undercover drug bust for selling oxycodone and marijuana. He's facing 3 felonies.

Harris will now be held without bail until a hearing later this month.