(a) The board shall fix and determine by appropriate rules and regulations how much service in any year is equivalent to one year of membership service, but in no case shall more than one year of service be creditable for all service in one calendar year. In developing rules and regulations to determine how much service in any year is equivalent to one year of membership service, the board shall be guided by the nature of the employment being considered and the number of months, weeks, days, and hours normally worked to carry out the normal duties associated with the employment. Service rendered for a regular school year shall be equivalent to one year of service in any case.

(b) Under such rules and regulations as the board shall adopt, each member who was a public school employee at any time from July 1, 1945, until the commencement date shall be entitled to file a detailed statement of all services as a public school employee rendered by him prior to the commencement date and for which he claims credit. If any person who would otherwise have qualified under this subsection is on leave in the armed forces of the United States, such person shall have six months after termination of his military service to qualify under this subsection for prior service credit. Upon verification of such statement of service, the board shall issue a prior service certificate based on the member's statement of service and certifying to the member the period of service prior to the commencement date with which he is credited. As long as a membership continues, a prior service certificate shall be final and conclusive proof of such service for retirement purposes. A member may within one year from the date of issuance or modification of his prior service certificate request the board to modify or correct such certificate. When membership ceases, such prior service certificate shall become void.

(c) Creditable service at retirement on which the retirement allowance of a member shall be based shall consist of the membership service rendered by him since he last became a member and, if he has a prior service certificate in full force and effect, the amount of the service certified on his prior service certificate.

(d) Any person who leaves public school employment at any time after January 1, 1970, to enter military service may return to public school employment at any time within five years after being released from military service and shall receive credit for such active military service upon the payment of employee contributions which would have been paid during his absence while in military service, plus the regular interest that would have accrued on such contributions.

(e) Any person who left public school employment to enter military service at any time prior to January 1, 1970, and returned to public school employment within five years after being released from military service shall receive credit for such active military service upon the payment of employee contributions that would have been paid during his absence while in service, plus the regular interest that would have accrued on such contributions.

(f) Any provision of this chapter to the contrary notwithstanding, any person, who was at least 65 years of age on June 30, 1970, and who would have been able to establish a minimum of ten years of prior service credit under this chapter if he had been employed as a public school employee on January 1, 1970, may be employed as a public school employee at any time during the period beginning July 1, 1974, and ending December 31, 1974. Upon becoming employed as a public school employee during such period of time, such person shall become a member and may establish prior service credit under subsection (b) of this Code section, notwithstanding the fact that he was not a public school employee at any time between January 1, 1970, and July 1, 1970. On or before June 1, 1974, the board shall inform all public school systems in this state of the contents of this subsection.

(g) Any provision of this chapter to the contrary notwithstanding, any person who was 60 years of age or older on January 1, 1975, who on January 1, 1970, had at least 14 years of service as a public school employee and who becomes employed as a public school employee at any time during the period beginning with March 26, 1975, and ending July 1, 1975, shall become a member and may establish prior service credit under subsection (b) of this Code section, notwithstanding the fact that he was not a public school employee at any time between January 1, 1970, and July 1, 1970. The board shall inform all public school systems in this state of the contents of this subsection by March 26, 1975.

(h) Any provision of this chapter to the contrary notwithstanding, any person who was at least 55 years of age on June 30, 1970, and who would have been able to establish a minimum of ten years of prior service credit under this chapter if he had been employed as a public school employee on January 1, 1970, may be employed as a public school employee at any time during the period beginning July 1, 1977, and ending December 31, 1980. Upon becoming employed as a public school employee during such period of time, such person shall become a member and may establish prior service credit under subsection (b) of this Code section, notwithstanding the fact that he was not a public school employee at any time between January 1, 1970, and July 1, 1970. On or before June 1, 1977, the board shall inform all public school systems in this state of the contents of this subsection.

(i) Any member who, if credited with service rendered prior to January 1, 1970, would have at least ten years of creditable service shall receive prior service credit for all service as a public school employee rendered by him at any time between January 1, 1945, and January 1, 1970.

(j) Any member who was a member of the Teachers Retirement System of Georgia because the member held a position which required membership in that retirement system and who, during membership in said teachers retirement system, also held a position as a public school employee for which creditable service under this retirement system has not been obtained shall have the right to obtain credit for such prior service as a public school employee by paying to the board of trustees the employee contributions that would have been paid to this retirement system during the period of such prior service plus regular interest thereon compounded annually from the time the prior service was rendered until the date of payment. Any member wishing to obtain credit for prior service under this subsection shall apply therefor to the board of trustees.