(a) Requirements for allowance of $800 or $1,600 exemption. Except as otherwise provided in this paragraph or in paragraph (b) of this section, the $800 or $1,600 exemption for articles acquired abroad will not be allowed unless the returning resident has remained beyond the territorial limits of the United States for a period of not less than 48 hours. The $800 exemption may be allowed on articles acquired abroad by a returning resident arriving directly from Mexico without regard to the length of time the person has remained outside the territorial limits of the United States.

(b) Not required for allowance of $1,600 exemption on return from the Virgin Islands. The $1,600 exemption applicable in the case of the arrival of a returning resident directly or indirectly from the Virgin Islands of the United States may be allowed without regard to the length of time such person has remained outside the territorial limits of the United States.

(c) Computation of time. The 48-hour period a returning resident must have completed abroad to be entitled to an exemption will be computed exactly. For example, a resident leaving United States territory at 1:30 p.m. on June 1 would complete the 48-hour period at 1:30 p.m. on June 3.