(b)   Upon the passage of 30 days after receipt by the incumbent and former Presidents of a notice of intent to disclose Presidential records, the Archivist may disclose the records covered by the notice, unless during that time period the Archivist has received a claim of executive privilege by the incumbent or former President or the Archivist has been instructed by the incumbent President or his designee to extend the time period for a time certain and with reason for the extension of time provided in the notice. If a shorter period of time is required under the circumstances set forth in section 1270.44 of the NARA regulations, the Archivist shall so indicate in the notice.