40 CFR §23.7

Unless the Administrator otherwise explicitly provides in a particular promulgation action or determination, the time and date of the Administrator's promulgation, issuance, or determination for purposes of section 1448(a)(2) shall be at 1:00 p.m. eastern time (standard or daylight, as appropriate) on the date that is (a) for a Federal Register document, two weeks after the date when the document is published in the Federal Register or (b) for any other document, two weeks after it is signed.