N.Y. Comp. Codes R. & Regs. tit. 4 § 5.4
A permanent employee who has resigned from his position may be reinstated, without exami nation, within one year from the date of such resignation in the position from which he resigned, if then vacant, or in any vacant position to which he was eligible for transfer or reassignment. In computing the one-year period within which a person may be reinstated after resignation, the day the resignation takes effect, any time spent in active service in the military or naval forces of the United States or of the State of New York, and any time served in another position in the civil service of the same governmental jurisdiction shall not be counted. In an exceptional case, the commission may, for good cause shown and where the interests of the government would be served, waive the provisions of this section to permit the reinstatement of a person to his former position more than one year after resignation. For the purpose of this section, where an employee on leave of absence resigns, such resignation shall be deemed effective as of the date of the commencement of such leave.
N.Y. Comp. Codes R. & Regs. Tit. 4 § 5.4