(a) Separate maintenance allowance rates are paid from the employee's date of arrival at Johnston Island to the employee's date of departure from Johnston Island. No deductions are necessary for details away from Johnston Island or for partial days. The separate maintenance allowance shall be computed and paid at daily rates as follows:

(1) Divide the annual rate of payment by the number of days in the applicable calendar year to obtain a daily rate (counting one half-cent and over as a whole cent);

(2) Multiply the daily rate by 14 to obtain a biweekly rate; and

(3) Multiply the daily rate by the number of days involved to obtain the rate for any period.

(b) A separate maintenance allowance is not part of an employee's rate of basic pay for any purpose.

(c) The rate for any pay period shall be computed at the daily rate applicable on the first day of that pay period.