N.J. Stat. Ann. § 2A:164-24

The board of chosen freeholders of any county, or the committee on the discharge of prisoners of such board, may, upon the recommendation of the sheriff or jail warden of the county jail or penitentiary in whose custody any prisoner may be, remit for good conduct from the sentence of any person committed to such county jail or penitentiary, a term not exceeding 1 day for every 6 days of such sentence. If any such person shall be again convicted and sentenced to imprisonment in such county jail or penitentiary, he may, in addition to such new sentence, be required at the discretion of the court to serve out the number of days remitted to him on the previous term.