Because the National Institute of Standards and Technology is one of two official timekeepers for the United States (the U.S. Naval Observatory is the other atomic clock operator), the agency's research library often addresses questions on how to correctly express times and dates.

Recently, the NIST librarians were asked to tackle the issue of whether 1999 should be written as MCMXCIX or MIM. Their response was that while MIM is more convenient, MCMXCIX probably will be favored because of earlier precedents with numbers such as 49 (written as XLIX rather than IL); however, the librarians point out that purists will use neither MIM nor MCMXCIX, opting instead for MCMXCVIIII. The ancient Romans, they explain, did not use the 20th century convention of IX for the number nine.

Calls to the U.S. Copyright Office, the Motion Picture Association of America, the Directors Guild of America and the American Institute of Architects revealed none of the bodies controlling copyright notices, film credits and cornerstone inscriptions -- all of which use Roman numeral dates -- has an action plan for dealing with the "year 1999 problem."