The DATFMT keyword specifies the internal date format for date literals and the default internal format for date fields within the program. You can specify a different internal date format for a particular field by specifying the format with the DATFMT keyword on the definition specification for that field.
The default date format for definitions can be temporarily
changed using the /SET and /RESTORE directives.
See /SET.
If the DATFMT keyword is not specified, the *ISO format is assumed. For more information on internal formats, see Internal and External Formats. Table 1 describes the various date formats and their separators.