A notice of hearing or of opportunity to be heard, required or authorized to be given by an Act of Congress, or which may otherwise properly be given, shall be deemed to have been given to all persons residing within the States of the Union and the District of Columbia, except in cases where notice by publication is insufficient in law, when the notice is published in the Federal Register at such a time that the period between the publication and the date fixed in the notice for the hearing or for the termination of the opportunity to be heard is—

((1)) not less than the time specifically prescribed for the publication of the notice by the appropriate Act of Congress; or

((2)) not less than fifteen days when time for publication is not specifically prescribed by the Act, without prejudice, however, to the effectiveness of a notice of less than fifteen days where the shorter period is reasonable.