Lindsay Lohan must report to the county jail by November 9th to serve 30-days behind bars, RadarOnline.com has learned.

Los Angeles Judge Stephanie Sautner made the ruling on Wednesday after determining that the Mean Girls star violated the terms of her probation stemming from her shoplifting conviction.

Prior to the judge making her ruling, Lohan -- wearing a polka dot dress with her hair pulled back in court  --  admitted in court that she did in fact violate the terms of her probation.