This document covers various aspects concerning the handling of date information in Natural applications.
The following topics are covered:
If you wish the value of a date field to be output in a specific representation, you usually specify an edit mask for the field. With an edit mask, you determine character by character what the output is to look like.
If you wish to use the current date in a specific representation, you need not define a date field and specify an edit mask for it; instead you can simply use a date system variable. Natural provides various date system variables, which contain the current date in different representations. Some of these representations contain a 2-digit year, some a 4-digit year.
For more information and a list of all date system variables, see the System Variables documentation.
The profile parameter DTFORM determines the default format used for dates
as part of the default title on Natural reports, for date constants and for date
input.
This date format determines the sequence of the day, month and year components of a date, as well as the delimiter characters to be used between these components.
Possible DTFORM settings are:
| Setting | Date Format1 | Example2 |
|---|---|---|
DTFORM=I
|
yyyy-mm-dd
|
2014-01-31 |
DTFORM=G
|
dd.mm.yyyy
|
31.01.2014 |
DTFORM=E
|
dd/mm/yyyy
|
31/01/2014 |
DTFORM=U
|
mm/dd/yyyy
|
01/31/2014 |
1
dd = day,
mm = month,
yyyy = year
2 assumed that DF or DFTITLE is set to L
The DTFORM parameter can be set in the Natural parameter
module/file or dynamically when Natural is invoked. By default,
DTFORM=I applies.
If an edit mask is specified, the representation of the field value is determined by the
edit mask. If no edit mask is specified, the representation of the field value is
determined by the session parameter DF in combination with the profile parameter
DTFORM.
With the DF parameter, you can choose one of the following date
representations:
For each representation, the sequence of the day, month and year components, and the
delimiter characters used are determined by the DTFORM parameter.
By default, DF=S applies (except for INPUT statements; see
below).
The session parameter DF is evaluated at compilation.
It can be specified with the following statements:
INPUT, DISPLAY, WRITE and PRINT at statement and element
(field) level,
MOVE, COMPRESS, STACK, RUN and FETCH at element (field) level.
When specified in one of these statements, the DF parameter applies to the following:
| Statement | Effect of DF parameter |
|---|---|
DISPLAY, WRITE, PRINT
|
When the value of a date variable is output with one of these statements, the
value is converted to an alphanumeric representation before it is output. The
DF parameter determines which representation is
used.
|
MOVE, COMPRESS
|
When the value of a date variable is transferred to an alphanumeric field
with a MOVE or COMPRESS statement, the value is
converted to an alphanumeric representation before it is transferred. The
DF parameter determines which representation is
used.
|
STACK, RUN, FETCH
|
When the value of a date variable is placed on the stack, it is converted to
alphanumeric representation before it is placed on the stack. The DF
parameter determines which representation is used.
The same applies when a date
variable is specified as a parameter in a |
INPUT
|
When a data variable is used in an INPUT statement, the
DF parameter determines how a value must be entered in
the field.
However, when a date variable for which no
|
Note:
With DF=S, only 2 digits are provided for the year information; this
means that if a date value contained the century, this information would be lost during
the conversion. To retain the century information, you set DF=I or
DF=L.
These examples assume that DTFORM=G applies.
/* DF=S (default) WRITE *DATX /* Output has this format: dd.mm.yy END
FORMAT DF=I WRITE *DATX /* Output has this format: ddmmyyyy END
FORMAT DF=L WRITE *DATX /* Output has this format: dd.mm.yyyy END
This example assumes that DTFORM=E applies.
DEFINE DATA LOCAL 1 #DATE (D) INIT <D'31/01/2014'> 1 #ALPHA (A10) END-DEFINE ... MOVE #DATE TO #ALPHA /* Result: #ALPHA contains 31/01/14 MOVE #DATE (DF=I) TO #ALPHA /* Result: #ALPHA contains 31012014 MOVE #DATE (DF=L) TO #ALPHA /* Result: #ALPHA contains 31/01/2014 ...
This example assumes that DTFORM=I applies.
DEFINE DATA LOCAL 1 #DATE (D) INIT <D'2014-01-31'> 1 #ALPHA1(A10) 1 #ALPHA2(A10) 1 #ALPHA3(A10) END-DEFINE ... STACK TOP DATA #DATE (DF=S) #DATE (DF=I) #DATE (DF=L) ... INPUT #ALPHA1 #ALPHA2 #ALPHA3 ... /* Result: #ALPHA1 contains 14-01-31 /* #ALPHA2 contains 20140131 /* #ALPHA3 contains 2014-01-31 ...
This example assumes that DTFORM=I applies.
DEFINE DATA LOCAL
1 #DATE1 (D)
1 #DATE2 (D)
1 #DATE3 (D)
1 #DATE4 (D)
END-DEFINE
...
INPUT #DATE1 (DF=S) /* Input must have this format: yy-mm-dd
#DATE2 (DF=I) /* Input must have this format: yyyymmdd
#DATE3 (DF=L) /* Input must have this format: yyyy-mm-dd
#DATE4 /* Input must have this format: yy-mm-dd or yyyymmdd
...
The session/profile parameter DFOUT only applies to date fields in INPUT, DISPLAY, WRITE and PRINT statements for which no edit mask is specified, and for
which no DF parameter
applies.
For date fields which are displayed by INPUT, DISPLAY,
PRINT and WRITE statements and for which neither an edit mask
is specified nor a DF parameter applies, the profile/session
parameter DFOUT determines the format in which the field values are
displayed.
With the DFOUT parameter, you can choose one of the following date
representations:
DFOUT=S |
8-byte representation with a 2-digit year and delimiters. Example:
yy-mm-dd.
|
DFOUT=I |
8-byte representation with a 4-digit year and no delimiters. Example:
yyyymmdd.
|
By default, DFOUT=S applies.
For each representation, the sequence of the day, month and year components and the
delimiter characters used (if so) are determined by the DTFORM parameter.
The lengths of the date fields are not affected by the DFOUT
setting, as either date value representation fits into an 8-byte field.
The DFOUT parameter can be set in the Natural parameter
module/file, dynamically when Natural is invoked, or at session level with the system command GLOBALS. It is evaluated
at runtime.
This example assumes that DTFORM=I
applies.
DEFINE DATA LOCAL
1 #DATE (D) INIT <D'2014-01-31'>
END-DEFINE
...
WRITE #DATE /* Output if DFOUT=S is set ...: 14-01-31
/* Output if DFOUT=I is set ...: 20140131
WRITE #DATE (DF=L) /* Output (regardless of DFOUT): 2014-01-31
...
The session/profile parameter DFSTACK only applies to date fields used in
STACK, FETCH and RUN statements for which no DF parameter has been
specified.
The DFSTACK parameter determines the format in which the values of
date variables are placed on the stack via a STACK, RUN or
FETCH statement.
The DFSTACK parameter can be set in the Natural parameter
module/file, dynamically when Natural is invoked, or at session level with the system command GLOBALS. It is
evaluated at runtime.
Possible DFSTACK settings are:
DFSTACK=S
|
8-byte date variables are placed on the stack with a 2-digit year and
delimiters. Example: yy-mm-dd.
|
DFSTACK=C
|
Same as DFSTACK=S. However:
Natural issues a runtime error if
the date value to be stacked would result in a century different from that of
the original value, either because of the |
DFSTACK=I
|
8-byte date variables are placed on the stack with a 4-digit year and no
delimiters. Example: yyyymmdd.
|
By default, DFSTACK=S applies.
For each date representation, the sequence of the day, month and year components and the
delimiter characters used (if so) are determined by the DTFORM parameter.
This example assumes that DTFORM=I
and YSLW=0 apply.
DEFINE DATA LOCAL 1 #DATE (D) INIT <D'2014-01-31'> 1 #ALPHA1(A8) 1 #ALPHA2(A10) END-DEFINE ... STACK TOP DATA #DATE #DATE (DF=L) ... INPUT #ALPHA1 #ALPHA2 ... /* Result if DFSTACK=S or =C is set: #ALPHA1 contains 14-01-31 /* Result if DFSTACK=I is set .....: #ALPHA1 contains 20140131 /* Result (regardless of DFSTACK) .: #ALPHA2 contains 2014-01-31 ...
The profile parameter YSLW allows you determine the century of a 2-digit
year value.
The YSLW parameter can be set in the Natural parameter module/file
or dynamically when Natural is invoked. It is evaluated at runtime when an alphanumeric
date value with a 2-digit year is moved into a date variable. This applies to data values
which are:
used with the mathematical
function
VAL(field),
used with the IS(D) option in a logical condition,
read from the stack as input data, or
entered in an input field as input data.
The YSLW parameter determines the range of years covered by a
so-called "year sliding window". The sliding-window mechanism assumes a date
with a 2-digit year to be within a "window" of 100 years. Within these 100
years, every 2-digit year value can be uniquely related to a specific century.
With the YSLW parameter, you determine how many years in the past
that 100-year range is to begin: The YSLW value is subtracted from
the current year to determine the first year of the window range.
Possible values of the YSLW parameter are 0 to 99. The default
value is YSLW=0, which means that no sliding-window mechanism is
used; that is, a date with a 2-digit year is assumed to be in the current century.
If the current year is 2014 and you specify YSLW=40, the sliding
window will cover the years 1974 to 2073. A 2-digit year value
nn from 74 to 99 is interpreted accordingly as
19nn, while a 2-digit year value
nn from 00 to 73 is interpreted as
20nn.
If the current year is 2014 and you specify YSLW=20, the sliding window will
cover the years 1994 to 2093. A 2-digit year value nn from 94
to 99 is interpreted accordingly as 19nn, while a 2-digit year
value nn from 00 to 93 is interpreted as
20nn.
The following examples illustrate the effects of using various combinations of the
parameters DFSTACK
and YSLW.
Note:
All these examples assume that DTFORM=I applies.
This example assumes the current year to be 2014, and that the parameter settings
DFSTACK=S (default) and
YSLW=20 apply.
DEFINE DATA LOCAL 1 #DATE1 (D) INIT <D'1956-12-31'> 1 #DATE2 (D) END-DEFINE ... STACK TOP DATA #DATE1 /* century information is lost (year 56 is stacked) ... INPUT #DATE2 /* year sliding window determines 56 to be 2056 ... /* Result: #DATE2 contains 2056-12-31
In this case, the year sliding window is not set appropriately, so that the century information is (inadvertently) changed.
This example assumes the current year to be 2014, and that the parameter settings
DFSTACK=S (default) and
YSLW=60 apply.
DEFINE DATA LOCAL 1 #DATE1 (D) INIT <D'1956-12-31'> 1 #DATE2 (D) END-DEFINE ... STACK TOP DATA #DATE1 /* century information is lost (year 56 is stacked) ... INPUT #DATE2 /* year sliding window determines 56 to be 1956 ... /* Result: #DATE2 contains 1956-12-31
In this case, the year sliding window is set appropriately, so that the original century information is correctly restored.
This example assumes the current year to be 2014, and that the parameter settings
DFSTACK=C and
YSLW=0 (default) apply.
DEFINE DATA LOCAL 1 #DATE1 (D) INIT <D'1956-12-31'> 1 #DATE2 (D) END-DEFINE ... STACK TOP DATA #DATE1 /* century information is lost (year 56 is stacked) ... INPUT #DATE2 /* 56 is assumed to be in current century -> 2056 ... /* Result: NAT1130 runtime error (Unintended century switch...)
In this case, the century information is (inadvertently) changed. However, this change is
intercepted by the DFSTACK=C setting.
This example assumes the current year to be 2014, and that the parameter settings
DFSTACK=C and
YSLW=60 apply.
DEFINE DATA LOCAL 1 #DATE1 (D) INIT <D'2056-12-31'> 1 #DATE2 (D) END-DEFINE ... STACK TOP DATA #DATE1 /* century information is lost (year 56 is stacked) ... INPUT #DATE2 /* year sliding window determines 56 to be 1956 ... /* Result: NAT1130 runtime error (Unintended century switch...)
In this case, the century information is changed due to the year sliding window. However,
this change is intercepted by the DFSTACK=C setting.
For information on this topic, see the description of the profile parameter YSLW.
The session/profile parameter DFTITLE determines the format of the date in a
default page title (as output with a
DISPLAY, WRITE or PRINT statement).
With the DFTITLE parameter, you can choose one of the following
date representations:
DFTITLE=S
|
8-byte representation with a 2-digit year and delimiters. Example:
yy-mm-dd.
|
DFTITLE=L
|
10-byte representation with a 4-digit year and delimiters. Example:
yyyy-mm-dd.
|
DFTITLE=I |
8-byte representation with a 4-digit year and no delimiters. Example:
yyyymmdd.
|
For each DFTITLE setting, the sequence of the day, month and year
and the delimiter characters used are determined by the DTFORM parameter.
The DFTITLE parameter can be set in the Natural parameter
module/file, dynamically when Natural is invoked, or at session level with the system command GLOBALS. It is evaluated
at runtime.
This example assumes that DTFORM=I applies.
WRITE 'HELLO' END /* /* Date in page title if DFTITLE=S is set ...: 14-01-31 /* Date in page title if DFTITLE=L is set ...: 2014-01-31 /* Date in page title if DFTITLE=I is set ...: 20140131
Note:
The DFTITLE
parameter has no effect on a user-defined page title as specified with a WRITE
TITLE statement.