Any commissioned officer of the National Oceanic and Atmospheric Administration promoted to a higher grade at any time after December 7, 1941, shall be deemed for all purposes to have accepted his promotion to higher grade upon the date such promotion is made by the President unless he shall expressly decline such promotion, and shall receive the pay and allowances of the higher grade from such date unless he is entitled under some other provision of law to receive the pay and allowances of the higher grade from an earlier date. No such officer who shall have subscribed to the oath of office required by section 3331 of title 5, shall be required to renew such oath or to take a new oath upon his promotion to a higher grade, if his service after the taking of such an oath shall have been continuous.