12. Any employee is deemed to have ceased to hold employment with the employer on the day following, whichever comes first,
(1) the effective date of his resignation;
(2) the date of his dismissal;
(3) the date of his retirement;
(4) the date of his death;
(5) the date of surrendering his position;
(6) the effective date of the abolition of his office.
Notwithstanding the foregoing, an employee who is suspended or is absent without authorization is deemed to have ceased to hold employment on the effective date of his suspension by his employer or his unauthorized absence, unless he is subsequently reinstated in his employment.