The appointing authority may, in its discretion, grant sick leave at half-pay for personal illness to a permanent employee having not less than one year of service after all of his sick leave, vacation and overtime credits have been used; provided, however, that the cumulative total of all sick leave at half-pay hereafter granted to any employee during his State service shall not exceed one pay period for each completed six months of his State service.
N.Y. Comp. Codes R. & Regs. Tit. 4 § 21.5