S.C. Code Ann. § 24-13-40

The computation of the time served by prisoners under sentences imposed by the courts of this State must be calculated from the date of the imposition of the sentence. However, when (a) a prisoner shall have given notice of intention to appeal, (b) the commencement of the service of the sentence follows the revocation of probation, or (c) the court shall have designated a specific time for the commencement of the service of the sentence, the computation of the time served must be calculated from the date of the commencement of the service of the sentence. In every case in computing the time served by a prisoner, full credit against the sentence must be given for time served prior to trial and sentencing, and may be given for any time spent under monitored house arrest. Provided, however, that credit for time served prior to trial and sentencing shall not be given: (1) when the prisoner at the time he was imprisoned prior to trial was an escapee from another penal institution; (2) when the prisoner is serving a sentence for one offense and is awaiting trial and sentence for a second offense in which case he shall not receive credit for time served prior to trial in a reduction of his sentence for the second offense; (3) when the prisoner commits a subsequent crime while out on bond; or (4) has bond revoked on any charge prior to trial or plea.