69.—Where a man of the Permanent Defence Force enlisted under F62[section 53 or 53A] deserts or absents himself without leave, whether once or oftener, then, save as may be otherwise prescribed, each period commencing on the date on which he deserts or absents himself without leave and ending on the date on which he next surrenders himself or reports back for duty or is apprehended (as the case may be) shall be excluded in reckoning his service in the Permanent Defence Force for the purposes of this Act.