To add or subtract time from a date in a SAS data step, we can use the SAS **intnx()** function.

```
data data_new;
set data;
date_plus_1_day = intnx('day', date_variable, 1, 'same');
date_plus_1_mon = intnx('month', date_variable, 1, 'same');
date_plus_1_yr = intnx('year', date_variable, 1, 'same');
run;
```

When working with dates in our data, it’s very useful to be able to easily add or subtract time to our date variables.

The SAS **intnx()** function allows us to add and subtract time very easily. We can add and subtract time by a given interval (second, minute, hour, day, week, month, year). In addition, we can adjust dates to the beginning or end of an interval if necessary.

From the documentation, the SAS intnx() function takes 3 arguments, ‘interval’, ‘start-form’, and ‘increment’, with an optional fourth argument ‘alignment’.

`INTNX(interval, start-from, increment <, 'alignment'>)`

The ‘interval’ is the interval you want to add or subtract (seconds, minutes, hours, days, weeks, months, years), ‘start-from’ is the date you will adjust, ‘increment’ is how many intervals you want to add or subtract, and ‘alignment’ is if you want to align the date to the beginning, middle, or end of the interval.

Let’s say we have the following SAS dataset with some date variables.

```
data data_with_dates;
input d :date9.;
format d date9.;
datalines;
31DEC2021
24OCT2020
12DEC2019
07JUN2019
17FEB2021
12JAN2021
03MAR2020
;
run;
```

Let’s add and subtract time from each of these variables – let’s add 1 day, add 3 months, add 2 years, and substract 4 weeks from each of the dates.

```
data date_new;
format d date9. d_plus_1_day date9. d_plus_3_mon date9. d_plus_2_yrs date9. d_minus_4_wk date9. ;
set data_with_dates;
d_plus_1_day = intnx('day', d, 1, 'same');
d_plus_3_mon = intnx('month', d, 3, 'same');
d_plus_2_yrs = intnx('year', d, 2, 'same');
d_minus_4_wk = intnx('week', d, -4, 'same');
run;
/* Output */
d d_plus_1_day d_plus_3_mon d_plus_2_yrs d_minus_4_wk
1 31DEC2021 01JAN2022 31MAR2022 31DEC2023 03DEC2021
2 24OCT2020 25OCT2020 24JAN2021 24OCT2022 26SEP2020
3 12DEC2019 13DEC2019 12MAR2020 12DEC2021 14NOV2019
4 07JUN2019 08JUN2019 07SEP2019 07JUN2021 10MAY2019
5 17FEB2021 18FEB2021 17MAY2021 17FEB2023 20JAN2021
6 12JAN2021 13JAN2021 12APR2021 12JAN2023 15DEC2020
7 03MAR2020 04MAR2020 03JUN2020 03MAR2022 04FEB2020
```

## Get Beginning or End of Interval with SAS intnx()

With the SAS **intnx()**, we can easily adjust dates to the beginning, middle or end of an interval with the ‘alignment’ argument.

Let’s say we have the same dataset as above. Let’s get the beginning of the month for each of the days in the dataset, as well as the end of the month for each date.

The following SAS code and output shows how easy it is to get the beginning and end of the month for each of the dates.

```
data date_new;
format d date9. d_mon_beg date9. d_mon_end date9.;
set data_with_dates;
d_mon_beg = intnx('month', d, 0, 'begin');
d_mon_end = intnx('month', d, 0, 'end');
run;
/* Output */
d d_mon_beg d_mon_end
1 31DEC2021 01DEC2021 31DEC2021
2 24OCT2020 01OCT2020 31OCT2020
3 12DEC2019 01DEC2019 31DEC2019
4 07JUN2019 01JUN2019 30JUN2019
5 17FEB2021 01FEB2021 28FEB2021
6 12JAN2021 01JAN2021 31JAN2021
7 03MAR2020 01MAR2020 31MAR2020
```

## Using SAS intnx() in a Loop to Create New Dates

If you are working as an analyst trying to forecast data with a model, the SAS **intnx()** function is very useful.

Let’s say we have a simple sales model which projects an increase of 10% in sales each year. Let’s say we have a dataset where we’d like to project out sales for the next 5 years.

We can use our simple sales model to create a forecast dataset very easily with the help of the SAS **intnx()** function.

```
data current_sales;
input d :date9. sales;
format d date9.;
datalines;
31DEC2021 100
;
run;
```

To forecast our data for 5 years, we will use a simple loop and **intnx()**.

```
data forecast_sales(drop=d i);
format forecast_date date9.;
set current_sales;
do i = 1 to 5;
forecast_date = intnx("year", d, i,"end");
sales = sales * 1.1;
output;
end;
run;
/* Output */
forecast_date sales
1 31DEC2022 110
2 31DEC2023 121
3 31DEC2024 133.1
4 31DEC2025 146.41
5 31DEC2026 161.051
```

## How to Add Days to SAS Date Variable with SAS intnx()

To add days to a SAS date variable, we can use the **SAS intnx()** function. We pass ‘day’ to the ‘interval’ argument in the **intnx()** function.

`intnx("day", date_variable, number_of_days);`

## How to Add Weeks to SAS Date Variable with SAS intnx()

To add weeks to a SAS date variable, we can use the **SAS intnx()** function. We pass ‘week’ to the ‘interval’ argument in the **intnx()** function.

`intnx("week", date_variable, number_of_weeks);`

## How to Add Months to SAS Date Variable with SAS intnx()

To add months to a SAS date variable, we can use the **SAS intnx()** function. We pass ‘month’ to the ‘interval’ argument in the **intnx()** function.

`intnx("month", date_variable, number_of_months);`

## How to Add Quarters to SAS Date Variable with SAS intnx()

To add quarters to a SAS date variable, we can use the **SAS intnx()** function. We pass ‘qtr’ to the ‘interval’ argument in the **intnx()** function.

`intnx("qtr", date_variable, number of quarters);`

## How to Add Years to SAS Date Variable with SAS intnx()

To add years to a SAS date variable, we can use the **SAS intnx()** function. We pass ‘year’ to the ‘interval’ argument in the **intnx()** function.

`intnx("year", date_variable, number_of_years);`

Hopefully this article has been useful for you to help you understand how to use the SAS **intnx()** function to increment the date for SAS date variables.

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