Q130444: HOWTO: Calculating Years, Months, and Days Between Two Dates

Article: Q130444
Product(s): Microsoft FoxPro
Version(s): MS-DOS:2.5,2.5a,2.5b,2.6,2.6a; WINDOWS:2.5,2.5a,2.5b,2.6,2.6a,3.0,6.0
Operating System(s): 
Keyword(s): kbvfp
Last Modified: 04-MAY-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 6.0 
- Microsoft FoxPro for Windows, versions 2.5, 2.5a, 2.5b, 2.6, 2.6a 
- Microsoft FoxPro for MS-DOS, versions 2.5, 2.5a, 2.5b, 2.6, 2.6a 
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SUMMARY
=======

The program in this article shows by example how to calculate the combination of
days, months, and years between two dates (starting date and ending date) passed
as date parameters.

NOTE: The starting date must be an earlier date than the ending date.

MORE INFORMATION
================

To run the program, save the following code as BTWNDATE.PRG. Then issue the
following command where startdate and enddate are date values:

  DO BTWNDATE.PRG WITH startdate, enddate

For example:

  DO BTWNDATE WITH {01/05/93},{01/05/95}

Code Sample
-----------

     *
     * BTWNDATE.PRG
     *

     PARAMETERS startdate, enddate
     IF startdate > enddate

          WAIT WINDOW "Start date must " + CHR(13) ;
          + "be earlier than End date"
          RETURN

     ENDIF
     IF PARAMETERS() <> 2

          WAIT WINDOW "Not Correct Number of Parameters"
          RETURN

     ENDIF

     PRIVATE  precmpdate, vyears, vmonths, vdays
     precmpdate={}
     vyears=0
     vmonths=0
     vdays=0
     
     * Calculate:
     *     endofmonth is the last day of month prior to month of enddate
     *
     
     endofmonth = CTOD(ALLTRIM(STR(MONTH(enddate))) + '/' + "01" + '/' + ;
     ALLTRIM(STR(YEAR(enddate)))) - 1
     *
     IF MONTH(startdate) <= MONTH(enddate)

          vyears = YEAR(enddate) - YEAR(startdate)
          IF DAY(startdate) <= DAY(enddate)
               vmonths = MONTH(enddate) - MONTH(startdate)
               vdays = DAY(enddate) - DAY(startdate)
          ELSE
               IF MONTH(startdate) = MONTH(enddate)
                    vyears = vyears - 1
               ENDIF
               vmonths = MOD(MONTH(enddate) - MONTH(startdate) - 1 + 12, 12)
               vdays = endofmonth - precmpdate + DAY(enddate)
          ENDIF

     ELSE

          vyears = YEAR(enddate) - YEAR(startdate) - 1
          IF DAY(startdate) > DAY(enddate)
               vmonths = MONTH(enddate) - MONTH(startdate) + 12 - 1
               vdays = endofmonth - precmpdate + DAY(enddate)
          ELSE
               vmonths = MONTH(enddate) - MONTH(startdate) + 12
               vdays = DAY(enddate) - DAY(startdate)
          ENDIF

     ENDIF
     CLEAR
     WAIT WINDOW  CHR(13) + ;
               '  Years: '  + STR(vyears) + CHR(13) + ;
               ' Months: ' + STR(vmonths) + CHR(13) + ;
               '   Days: ' + STR(vdays) + CHR(13) + ;
               CHR(13) + ;
               ' Between ' + DTOC(startdate) + CHR(13) +;
               '     and ' + DTOC(enddate)

     RETURN


Additional query words:

======================================================================
Keywords          : kbvfp 
Technology        : kbVFPsearch kbAudDeveloper kbFoxproSearch kbZNotKeyword3 kbFoxPro250DOS kbFoxPro250aDOS kbFoxPro250bDOS kbFoxPro260DOS kbFoxPro260aDOS kbFoxPro260 kbFoxPro250 kbFoxPro250a kbFoxPro250b kbFoxPro260a kbVFP300 kbVFP600
Version           : MS-DOS:2.5,2.5a,2.5b,2.6,2.6a; WINDOWS:2.5,2.5a,2.5b,2.6,2.6a,3.0,6.0
Issue type        : kbhowto

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