Calculate days and months between dates

[NewUsrStat]

Guys, 

I'm trying to perform a simple task. 

i have a data set with many columns. Among them two columns named: "Start" and "End". 

They contain date: e.g:

          ID                 Start                       End

       00001        12/01/2020             15/01/2020

       00001        20/01/2020             25/01/2020

       00001        30/01/2020            01/02/2020

       00002        02/02/2020            05/02/2020

       00002        06/02/2020            03/03/2020

       00003        01/05/2020            31/12/2020

       00004        01/07/2020            01/08/2020 

      ............      .................             .....................

I simply would like to count row-wise the days in the intervals and the months in the intervals of time from Start to End. I tried: 

data want;
set myinput;
format start end mmddyy10.;
months_diff = intck('months', start, end);

days_diff = intck('days', start, end);
run;

But it fails. For sure I'm wrong. 

Can anyone help me please? Thank you in advance

[Tom · Accepted solution]

You need to use the names of valid intervals with the iNTCK() function.  MONTH and DAY can work with DATE values.  But MONTHS and DAYS will not be understood. 

Note that for MONTH it counts the number of month boundaries crossed, which might not be what you want if any of your dates are not the first of them month.  You might try setting the fourth parameter to the function to 'same'.

Note for days you can just subtract as DATE values are numbers of days.

months_diff = intck('month', start, end,'same');
days_diff = end - start;

PS Displaying date in DMY or MDY order will confuse 50% of your audience.  Does 10/12 mean October Twelfth or the Tenth of December?

[NewUsrStat]

Thank you for help. it is what I received. The format is ddmmyy. So, 10/12 is December the 10th.