Overview of Date Functions
The following explains the difference between the types
of date functions:
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Standard date functions are for use with standard
date formats, or just date formats. A date format refers to internally
stored data that is capable of holding date components, such as
century, year, quarter, month, and day. It does not include time
components. A synonym does not specify an internal data type or
length for a date format. Instead, it specifies display date components,
such as D (day), M (month), Q (quarter), Y (2-digit year), or YY
(4-digit year). For example, format MDYY is a date format that has
three date components; it can be used in the USAGE attribute of a
synonym. A real date value, such as March 9, 2004, described by
this format is displayed as 03/09/2004, by default. Date formats
can be full component and non-full component. Full component formats
include all three letters, for example, D, M, and Y. JUL for Julian
can also be included. All other date formats are non-full component.
Some date functions require full component arguments for date fields,
while others will accept full or non-full components. A date format
was formerly called a smart date.
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Legacy date functions are for use with legacy dates only.
A legacy date refers to formats with date edit options, such as
I6YMD, A6MDY, I8YYMD, or A8MDYY. For example, A6MDY is a 6-byte
alphanumeric string. The suffix MDY indicates the order in which
the date components are stored in the field, and the prefix I or
A indicates a numeric or alphanumeric form of representation. For
example, a value '030599' can be assigned to a field with format
A6MDY, which will be displayed as 03/05/99.
Date formats have an internal representation matching either
numeric or alphanumeric format. For example, A6MDY matches alphanumeric
format, YYMD and I6DMY match numeric format. When function output
is a date in specified by output, it can be used either for
assignment to another date field of this format, or it can be used
for further data manipulation in the expression with data of matching
formats. Assignment to another field of a different date format,
will yield a random result.
All but three date functions deal with only one
date format. The exceptions are DATECVT, HCNVRT, and HDATE, which
convert one date type into another.