Within the respective zones created under the authority of sections 261 to 264 of this title the standard time of the zone shall insofar as practicable (as determined by the Secretary of Transportation) govern the movement of all common carriers engaged in interstate or foreign commerce. In all statutes, orders, rules, and regulations relating to the time of performance of any act by any officer or department of the United States, whether in the legislative, executive, or judicial branches of the Government, or relating to the time within which any rights shall accrue or determine, or within which any act shall or shall not be performed by any person subject to the jurisdiction of the United States, it shall be understood and intended that the time shall insofar as practicable (as determined by the Secretary of Transportation) be the United States standard time of the zone within which the act is to be performed.
15 U.S. Code § 262. Duty to observe standard time of zones
1966—Pub. L. 89–387 inserted “insofar as practicable (as determined by the Interstate Commerce Commission)” in two places and substituted “engaged in interstate or foreign commerce” for “engaged in commerce between the several States or between a State and any one of the Territories of the United States, or between a State or the Territory of Alaska and any one of the insular possessions of the United States or any foreign country”.