HDIFF: Finding the Number of Units Between Two Date-Time Values

Reference: Usage Notes for HDIFF

HDIFF does its subtraction differently from DATEDIF, which subtracts date components stored in date fields. The DATEDIF calculation looks for full years or full months. Therefore, subtracting the following two dates and requesting the number of months or years, results in 0:

DATE1 12/25/2014, DATE2 1/5/2015

Performing the same calculation using HDIFF on date-time fields results in a value of 1 month or 1 year as, in this case, the month or year is first extracted from each date-time value, and then the subtraction occurs.

Syntax: How to Find the Number of Units Between Two Date-Time Values

HDIFF(end_dt, start_dt, 'component', output)

where:

end_dt

Date-time

Is the date-time value to subtract from, the name of a date-time field that contains the value, or an expression that returns the value.

start_dt

Date-time

Is the date-time value to subtract, the name of a date-time field that contains the value, or an expression that returns the value.

component

Alphanumeric

Is the name of the component to be used in the calculation, enclosed in single quotation marks. If the component is a week, the WEEKFIRST parameter setting is used in the calculation.

output

Floating-point double-precision

Is the field that contains the result, or the format of the output value enclosed in single quotation marks. The format must be floating-point double-precision.

Example: Finding the Number of Days Between Two Date-Time Fields (Reporting)

HDIFF calculates the number of days between the TRANSDATE and ADD_MONTH fields and stores the result in DIFF_PAYS, which has the format D12.2:

TABLE FILE VIDEOTR2
PRINT CUSTID TRANSDATE AS 'DATE-TIME' AND COMPUTE
ADD_MONTH/HYYMDS = HADD(TRANSDATE, 'MONTH', 2, 8, 'HYYMDS');
DIFF_DAYS/D12.2 = HDIFF(ADD_MONTH, TRANSDATE, 'DAY', 'D12.2');
WHERE DATE EQ 2000;
END

The output is:

CUSTID  DATE-TIME         ADD_MONTH               DIFF_DAYS
------  ---------         ---------               ---------
1237    2000/02/05 03:30  2000/04/05 03:30:00     60.00
1118    2000/06/26 05:45  2000/08/26 05:45:00     61.00

Example: Finding the Number of Days Between Two Date-Time Fields (Maintain)

HDIFF calculates the number of days between ADD_MONTH and DT1:

MAINTAIN FILE DATETIME
FOR 1 NEXT ID INTO STK;
COMPUTE
NEW_DATE/HYYMDS = HADD(STK.DT1, 'MONTH', 2,10, NEW_DATE);
DIFF_DAYS/D12.2 = HDIFF(NEW_DATE,STK.DT1,'DAY', DIFF_DAYS);
TYPE "STK(1).DT1 = "STK(1).DT1;
TYPE "NEW_DATE = "NEW_DATE;
TYPE "DIFF_DAYS = "DIFF_DAYS
END