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TechTip: Elapsed Time Function

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If you're creating an application that has to calculate elapsed time based on a start and end time, you know what a challenging task this can be. Even with many of the date and time RPG op codes, this can often involve incorporating some ugly code into your application. To solve this problem, you can use the CalcElapsed ILE RPG user-defined function. I'll show you how this function works, how to create it, and how to incorporate it into your applications.

As you can see below in the source for this function's prototype, this function accepts five parameters. The first two parameters, start date and end date, are supplied as a date (D) data type. The next two parameters, start time and end time, are supplied as a time (T) data type. The fifth parameter is used to identify the data to be returned by the function.

     D CalcElapsed     PR            14  6         
     D  FromDate                       D   VALUE DATFMT(*ISO)
     D  ToDate                         D   VALUE DATFMT(*ISO)
     D  FromTime                       T   VALUE
     D  ToTime                         T   VALUE     
     D  Format                        1A   VALUE    


The value returned by the function will be a 14-digit number with six decimal places. The actual value returned depends on the value of the fifth parameter. If D is specified, the value returned represents the number of days. The decimal places represent the minutes and seconds as a decimal portion of a day; for example, 12 hours would be .5 days. If H is specified, the elapsed time is returned in hours. Again, the decimal portion would represent the minutes as a portion of an hour. The final option, L, returns a value whereby everything to the left of the decimal represents years, months, and days, and the numbers to the right of the decimal point represent hours minutes and seconds (yyyymmdd.hhmnss). For example, an elapsed time of 10 years, 3 months, 2 days, 5 hours and 15 minutes would be returned as 00100302.051500. The source for the CalcElapsed function itself is shown below.

 HDATFMT(*ISO) NOMAIN     
  *===============================================================  
  * Compile Command  
  *
  * Create Commands: CRTRPGMOD MODULE(library/CALCELAPSD)  
  *                            SRCFILE(library/QRPGLESRC)  
  *         
  *===============================================================  
 D/COPY QRPGLESRC,calcelappr   
 D Elapsed         S             14  6 
 D Elapsd2         S             15  0 
 D FrTimeSt        S             30A 
 D ToTimeSt        S             30A  
 D ZeroTime        S               Z   
 D EndStmp         S               Z   
 P CalcElapsed     B                   EXPORT  
 D CalcElapsed     PI            14  6    
 D  FromDate                       D   VALUE DATFMT(*ISO) 
 D  ToDate                         D   VALUE DATFMT(*ISO)  
 D  FromTime                       T   VALUE   
 D  ToTime                         T   VALUE    
 D  Format                        1A   VALUE   
  /Free                                
     FrTimeSt = %Char(FromDate) + '-' + %Char(FromTime) + '.00000'; 
     ToTimeSt = %Char(ToDate) + '-' + %Char(ToTime) + '.00000';  
   Select;   
   When Format='D'; 
        Elapsed=%Diff(%TimeStamp(ToTimeSt: *ISO):  
                %TimeStamp(FrTimeSt:*ISO): *SECONDS)/86400;  
   When Format='H';        
        Elapsed=%Diff(%TimeStamp(ToTimeSt: *ISO):  
                 %TimeStamp(FrTimeSt:*ISO): *SECONDS)/3600; 
   When Format='L';     
        Elapsd2=%Diff(%TimeStamp(ToTimeSt: *ISO):  
                %TimeStamp(FrTimeSt:*ISO): *SECONDS);  
        ZeroTime=*Loval;    
        EndStmp=ZeroTime + %Seconds(Elapsd2);  
        Elapsed=(%Subdt(EndStmp:*YEARS)-1)*10000;   
        Elapsed=Elapsed+(%Subdt(EndStmp:*MONTHS)-1)*100;   
        Elapsed=Elapsed+(%Subdt(EndStmp:*DAYS)-1);  
        Elapsed=Elapsed+%Subdt(EndStmp:*HOURS)*.01; 
        Elapsed=Elapsed+%Subdt(EndStmp:*MINUTES)*.0001;   
        Elapsed=Elapsed+%Subdt(EndStmp:*SECONDS)*.000001;  
   EndSl;        
   Return Elapsed; 
  /End-Free    
 P CalcElapsed     E     


This function takes the supplied date and time values and converts them to a Timestamp field. The %Diff ILE RPG function calculates the difference between the two timestamp values. This %Diff function can be used with two date fields, two time fields, two timestamp fields, a date field and a timestamp field, or a time field and timestamp field. This function is used as follows:

    Diff=%Diff(StartDate: EndDate: *DAYS)


This example would calculate the difference between the two supplied dates and return a value that represents the number of days between the two dates. In the CalcElapsed function, we use the *SECONDS option to calculate seconds between the two dates. Depending on the value of the Format parameter, this value will be divided by either 86,400 (the number of seconds in a day) when the format is D or 3,600 (the number of seconds in an hour) when the format is H. If the format is L, the calculation is a little more complicated. In this case, we need to determine the duration as a value of years, months, days, hours, minutes, and seconds. To do this, we again use the %DIFF function to determine the duration in the lowest level used by the application, which is seconds. Next, we add this value to a timestamp field that has been initialized to *LOVAL. We add the elapsed seconds field value using the %SECONDS BIF, which converts a numeric value to a format that can be added to a date, time, or timestamp field. This will result in a date that has been increased by the number of seconds specified. The resulting value is then divided into the required date and time pieces, which are then reassembled in a way that results in the value being returned as yyyymmdd.hhmnss.

Below is the source for a small RPG application that shows how to incorporate this function into your applications.


HDATFMT(*MDY)
D/COPY QRPGLESRC,calcelappr 
D  FromDate       S               D   DATFMT(*ISO)   
D  ToDate         S               D   DATFMT(*ISO) 
D  FromTime       S               T             
D  ToTime         S               T             
D Difference      S             30A               
C     *ENTRY        PLIST                                              
C                   PARM                    FDate             6  
C                   PARM                    TDate             6   
C                   PARM                    FTime             6   
C                   PARM                    TTime             6  
C                   PARM                    Fmt               1  
C     *MDY0         Move      FDate         FromDate    
C     *MDY0         Move      TDate         ToDate        
C     *HMS0         Move      FTime         FromTime      
C     *HMS0         Move      TTime         ToTime        
C                   Eval      Difference=%EDITC(CalcElapsed(FromDate: 
C                             ToDate:FromTime:ToTime:Fmt): 'M')   
C     Difference    Dsply                                 
C                   Return                                



This program accepts the same five parameters required by our function, except that the date and time values are supplied through an alpha field rather than through a date or time field. This program converts the values provided to date and time values and uses the Eval op code to access the CalcElapsed function for the supplied dates and times. The value returned by the function is edited using the %EDITC function. The resulting value is displayed to the workstation that executes the application.

Creating and incorporating the function into an application is a two-step process. First, you must create the RPG module for the function itself. This is done using the Create RPG Module (CRTRPGMOD) command shown below:

CRTRPGMOD MODULE(library/CALCELAPSD) SRCFILE(library/QRPGLESRC) 


In this example, library should be replaced with our source and/or program library. Next, we have to create the module for our test application. We again use the CRTRPGMOD command to do this:

CRTRPGMOD MODULE(library/TESTELAPSD) SRCFILE(library/QRPGLESRC) 


Once the two modules have been created, we can bind them together using the Create Program (CRTPGM) command:

CRTPGM PGM(MFAUST/TESTELAPSD) MODULE(MFAUST/TESTELAPDS MFAUST/CALCELAPSD)     


The resulting program would be called as shown below:

CALL PGM(TESTELAPSD) PARM('010401' '011502' '084515' '073000' 'L')          


This example is passing a start time and date of 8:45:14 a.m. on January 4, 2001, and an ending time and date of 7:30:00 a.m. on January 15, 2002. Below is a sample of the output displayed when this program is called. (Click image to enlarge.)

http://www.mcpressonline.com/articles/images/2002/elapsedt[1]V500.png

The value shown indicates a difference of 1 year, 10 days, 22 hours, 44 minutes, and 45 seconds from the start to the end.

Your specific needs may require modifications to this function. Maybe you need the option to get to duration in months or even weeks. Either of these could easily be added to our function by simple inserting some extra options for our Format value within the SELECT group. In any case, this function can help you save time. And now you can calculate just how much!

Mike Faust is MIS Manager for The Lehigh Group in Macungie, PA. Mike is also the author of The iSeries and AS400 Programmer's Guide to Cool Things from MC Press. You can contact Mike at This email address is being protected from spambots. You need JavaScript enabled to view it..

Mike Faust

Mike Faust is a senior consultant/analyst for Retail Technologies Corporation in Orlando, Florida. Mike is also the author of the books Active Server Pages Primer, The iSeries and AS/400 Programmer's Guide to Cool Things, JavaScript for the Business Developer, and SQL Built-in Functions and Stored Procedures. You can contact Mike at This email address is being protected from spambots. You need JavaScript enabled to view it..

MC Press books written by Mike Faust available now on the MC Press Bookstore.

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