You can use the INTCK function in SAS to quickly calculate the difference between two dates in SAS.

This function uses the following basic syntax:

INTCK(interval, start date, end data, method)

where:

• interval: Interval to calculate (day, week, month, year, etc.)
• start date: The start date
• end date: The end date
• method: Whether to count complete intervals (‘D’ = No (Default), ‘C’ = Yes)

The following example shows how to use this function in practice.

Example : Calculate Difference Between Dates in SAS

Suppose we have the following dataset in SAS that contains two date variables:

/*create dataset*/
data original_data;
    format start_date end_date date9.;
    input start_date :date9. end_date :date9.;
    datalines;
01JAN2022 09JAN2022
01FEB2022 22FEB2022 
14MAR2022 04APR2022
01MAY2022 14AUG2022
;
run;

/*view dataset*/
proc printdata=original_data;

We can use the following code to calculate the difference between the values in the start_date and end_date variables in days, weeks, and months:

/*create new dataset*/
data new_data;
    set original_data;
    days_diff = intck('day', start_date, end_date);
    weeks_diff = intck('weeks', start_date, end_date);
    months_diff = intck('months', start_date, end_date);
run;

/*view new dataset*/
proc printdata=new_data;

The three new variables show the difference between start_date and end_date in days, weeks, and months.

Note that we can use the ‘c‘ argument in the INTCK function to only calculate the difference in complete days, weeks, and months:

/*create new dataset*/
data new_data;
    set original_data;
    days_diff = intck('day', start_date, end_date, 'c');
    weeks_diff = intck('weeks', start_date, end_date, 'c');
    months_diff = intck('months', start_date, end_date, 'c');
run;

/*view new dataset*/
proc printdata=new_data;

In this table, the difference in weeks between Jan 1st and Jan 9th is calculated as 1 since only one whole week can fit between these dates.

However, in the previous table the difference in weeks was calculated as 2 since there were two partial weeks that fit between these two dates.

Additional Resources

The following tutorials explain how to perform other common tasks in SAS: