Date Variables
Date information was originally entered using separate date variables (year, month, day). In 1989, 1991, and 1993 files, these variables were concatenated to form 4- and 6-digit variables of the form YYMM and YYMMDD, where YY=year, MM=month, and DD=day. Although they are documented in the questionnaires, the original year, month, and day variables have been deleted from 1989, 1991, and 1993 data files.
Separate date variables (year, month, day) still exist in 1997 and 2000 files. The 1997 and 2000 year variables have the form YYYYS dates are used in the Master File.