In 1996, through the joint efforts of the Treasury, OMB, and GAO, a body of generally accepted accounting principles (GAAP) covering most transactions was promulgated for the Federal government.
The GAAP that covered most transactions was created in 1996.
In the 18th-century Baroque church, you may hear the nuns praying or singing, but you'll never see them; they are cloistered on the other side of the grillwork.