37 U.S.C. § 1004

A member of a uniformed service who is entitled to pay and allowances under this title for a continuous period of less than one month is entitled to his pay and allowances for each day of that period at the rate of ¹⁄₃₀ of the monthly amount of his pay and allowances. The thirty-first day of a calendar month may not be excluded from a computation under this section.