Getting ISODATE Formatted Output

SAS stores dates internally as the number of seconds since midnight, January 1, 1960. Dates before then are stored as negative numbers. The built-in variable <???> contains the current date and time in that format, as an integer quantity. (Actually, all quantities in SAS are stored as 64-bit floating-point numbers. This allows for 56 bits of precision, which avoids the 2037 problem that UNIX has with its 32-bit integer.)

SAS has several date and time format codes that will print these huge numbers as human-readable dates and times, but it does not have one for ISO format. You can construct a string variable containing the date in ISO format with the following SAS language commands:

(Under construction.)

SPSS stores dates internally as the number of seconds since midnight, October 14, 1582, which was the first day of the Gregorian Calendar. The built-in variable $time contains the current date and time in that format, as an integer quantity. (Actually, all quantities in SPSS are stored as 64-bit floating-point numbers. This allows for 56 bits of precision, which avoids the 2037 problem that UNIX has with its 32-bit integer.)

SPSS has several date and time format codes that will print these huge numbers as human-readable dates and times, such as DATE11 which is the British English literary style, but it does not have one for ISO format. You can construct a string variable containing the date in ISO format with the following SPSS language commands:

/* Assume the date is contained in SPSS variable "dt" */
STRING isodate (A10).
COMPUTE isodate = CONCAT(STRING(XDATE.YEAR(dt),N4.0),'-',
                         STRING(XDATE.MONTH(dt),N2.0),'-'
                         STRING(XDATE.MDAY(dt),N2.0)).

DATA LIST /
  #yr 1-4
  #mo 6-7
  #da 9-10.
COMPUTE dt = DATE.MDY(#mo,#da,#yr).
BEGIN DATA.
1998-06-23
2000-02-29
2001-01-02
END DATA.

      INTEGER DATP(8)
      CALL DATIM(DATP)
      WRITE (6,44) DATP(8),DATP(7),DATP(6)
   44 FORMAT(1X,I4.4,'-',I2.2,'-',I2.2)

To write this time stamp to a file in ISO format:

(Under construction.)

The Rexx DATE function returns the date in one of a variety of formats depending on the character constant you pass it. The default format, called Normal, is the British English literary format, "23 Jun 1998", reflecting the fact that Rexx's author, Mike Cowlishaw, is an Englishman. Some of Rexx's date formats should be avoided, such as Century, which gives day number within the century and will go to 0 in 2000, or Usa, which is the American mm/dd/yy, with a two-digit year. The Standard format, yyyymmdd, is the best, since it is very close to ISO. All we need to do is add the dashes. This is easily done by:

   isodate  = translate('year-mn-dt',date('S'),'yearmndt')

This page last updated 1998-09-25. Please send comments and reports of broken links to the author: Roger Deschner