Until converted under the provisions of this subchapter, any individual who is in the Foreign Service before February 15, 1981, and is serving under an appointment as a Foreign Service officer, Foreign Service information officer, Foreign Service Reserve officer with limited or unlimited tenure, or Foreign Service staff officer or employee, shall be treated for purposes of salary, allowances, and other matters as if such individual had been converted under section 4152 or 4153 of this title, as the case may be, on February 15, 1981, except that any adjustment of salary under this section shall take effect—

(1) in the case of an individual who is in the Foreign Service on October 17, 1980, on the first day of the first pay period which begins on or after October 1, 1980, and

(2) in the case of an individual who is appointed to the Foreign Service after October 17, 1980, on the date such appointment becomes effective.