Rational Developer for System z
Enterprise COBOL for z/OS, Version 4.1, Language Reference


Date field

A date field can be any of the following:

The term date field refers to both expanded date fields and windowed date fields.

Windowed date field

A windowed date field is a date field that contains a windowed year. A windowed year consists of two digits, representing a year within the century window.

Expanded date field

An expanded date field is a date field that contains an expanded year. An expanded year consists of four digits.

The main use of expanded date fields is to provide correct results when these are used in combination with windowed date fields; for example, where migration to four-digit year dates is not complete. If all the dates in an application use four-digit years, there is no need to use the millennium language extensions.

Year-last date field

A year-last date field is a date field whose DATE FORMAT clause specifies one or more Xs preceding the YY or YYYY. Year-last date fields are supported in a limited number of operations, typically involving another date with the same (year-last) date format, or a nondate.

Date format

Date format refers to the date pattern of a date field, specified either:

  • Explicitly, by the DATE FORMAT clause or DATEVAL intrinsic function argument-2
  • Implicitly, by statements and intrinsic functions that return date fields.

Compatible date field

The meaning of the term compatible, when applied to date fields, depends on the COBOL division in which the date field occurs:

Data division
Two date fields are compatible if they have identical USAGE and meet at least one of the following conditions:
  • They have the same date format.
  • Both are windowed date fields, where one consists only of a windowed year, DATE FORMAT YY.
  • Both are expanded date fields, where one consists only of an expanded year, DATE FORMAT YYYY.
  • One has DATE FORMAT YYXXXX, the other, YYXX.
  • One has DATE FORMAT YYYYXXXX, the other, YYYYXX.

A windowed date field can be subordinate to an expanded date group data item. The two date fields are compatible if the subordinate date field has USAGE DISPLAY, starts 2 bytes after the start of the group expanded date field, and the two fields meet at least one of the following conditions:

  • The subordinate date field has a DATE FORMAT pattern with the same number of Xs as the DATE FORMAT pattern of the group date field.
  • The subordinate date field has DATE FORMAT YY.
  • The group date field has DATE FORMAT YYYYXXXX and the subordinate date field has DATE FORMAT YYXX.
Procedure division
Two date fields are compatible if they have the same date format except for the year part, which can be windowed or expanded. For example, a windowed date field with DATE FORMAT YYXXX is compatible with:
  • Another windowed date field with DATE FORMAT YYXXX
  • An expanded date field with DATE FORMAT YYYYXXX

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