Astrometric data have been distributed via CD-ROM and are also available on the web pages. None of this data is sensitive to the Y2K problem. In most cases there is no calendar date associated with the data. They are usually reduced to a common epoch and equinox, eg. J2000.0 and it is up to the user to apply the proper formulae for converting to other times. In some cases an epoch is associated with observational data, eg. Washington Double Star Catalog. Since these data often span centuries they have always been given with the full year value. In observational catalogs where only two digits have been used, the dates are associated with a catalog epoch, so that it is unambiguous as to which century is involved, eg. the transit circle catalogs. Conversion of positions across centuries has often been required in the past and this is a standard operation. These catalogs are seldom used by end users.
Information about other USNO Y2K compliance, such as time and earth orientation, can be found at the top level USNO page.