5.3.6.1 "COBOL Language Reference" IBM Library Server

X 5.3.6.1 Semantics of Windowed Date Fields

X Windowed date fields undergo automatic expansion relative to the century
X window when they are used as operands in arithmetic expressions or
X arithmetic statements. However, the result of incrementing or
X decrementing a windowed date is still treated as a windowed date for
X further computation, comparison, and storing.

X When used in the following situations, windowed date fields are treated as
X if they were converted to expanded date format:

X Operands in subtractions in which the other operand is an expanded
X date
X Operands in relation conditions
| A sending field in arithmetic or MOVE statements

X The details of the conversion to expanded date format depend on whether
X the windowed date field is numeric or alphanumeric.

X Given a century window starting year of 19nn, the year part (yy) of a
X numeric windowed date field is treated as if it was expanded as follows:

X If yy is less than nn, then add 2000 to yy
X If yy is equal to or greater than nn, then add 1900 to yy

X For signed numeric windowed date fields, this means that there can be two
X representations of some years. For instance, windowed year values 99 and
X -01 are both treated as 1999, since 1900 + 99 = 2000 + -01.

X Alphanumeric windowed date fields are treated in a similar manner, but
X using a prefix of "19" or "20" instead of adding 1900 or 2000.

X For example, when used as an operand of a relation condition, a windowed
X date field defined by:

X 01 DATE-FIELD DATE FORMAT YYXXXX PICTURE 9(6) X VALUE IS 450101.

X is treated as if it was an expanded date field with a value of:

X 19450101, if the century window starting year is 1945 or earlier

X or
X 20450101, if the century window starting year is later than 1945

Subtopics:

5.3.6.1.1 Date Trigger Values (Host Only)

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X 5.3.6.1 Semantics of Windowed Date Fields

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