Every person convicted of a felony before October 1, 1942, except those referenced in § 53.1-194, shall, for every month that he is held in confinement after June 24, 1944, in any state correctional facility, without violating any prison rule or regulation, be allowed a credit of thirty days upon the total term of confinement to which he has been sentenced, in addition to the time he actually serves. Any credit allowed under the provisions of this section shall also be considered as reducing the term of imprisonment to which the prisoner was or is sentenced for the purpose of determining his eligibility for parole.
Va. Code § 53.1-193