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X 1.7 Millennium Language Extensions and Date Fields




X Many applications use 2 digits rather than 4 digits to represent the year
X in date fields, and assume that these values represent years from 1900 to
X 1999. This compact date format works well for the 1900s, but it does not
X work for the year 2000 and beyond because these applications interpret
X "00" as 1900 rather than 2000, producing incorrect results.


X The millennium language extensions are designed to allow applications that
X use 2-digit years to continue performing correctly in the year 2000 and
X beyond, with minimal modification to existing code. This is achieved
X using a technique known as windowing, which removes the assumption that
X all 2-digit year fields represent years from 1900 to 1999. Instead,
X windowing enables 2-digit year fields to represent years within any
X 100-year range, known as a century window.


X For example, if a 2-digit year field contains the value 15, many
X applications would interpret the year as 1915. However, with a century
X window of 1960-2059, the year would be interpreted as 2015.


X The millennium language extensions provide support for the most common
X operations on date fields: comparisons, moving and storing, incrementing
X and decrementing. This support is limited to date fields of certain
X formats; for details, see "DATE FORMAT Clause" in topic 5.3.6.


X For information on supported operations and restrictions when using date
X fields, see "Restrictions On Using Date Fields" in topic 5.3.6.2.

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