A prisoner shall not be discharged from the penitentiary of New Mexico or any other correctional facility until he has served the full term for which he was sentenced. The term shall be computed from and include the day on which his sentence took effect and shall exclude any time the convict may have been at large by reason of escape, unless he is pardoned or otherwise released by legal authority. The provisions of this section shall not be interpreted to deprive a prisoner of any reduction of time to which he may be entitled pursuant to the provisions of Sections 31-20-11, 31-20-12 and 33-2-34 N.M. Stat. Ann..