DATA Step, Macro, Functions and more

Calculate difference between dates in months with decimals

Reply
Contributor
Posts: 32

Calculate difference between dates in months with decimals

Hi! If I want to calculate the difference between months I use this syntax;

*months;
DATA want;
SET have;
months=intck("month", start, end);
RUN;

But you only get the months without decimals. Is there an easy way to get the months with for example 2 decimals?

Super User
Posts: 9,880

Re: Calculate difference between dates in months with decimals

Fractions of what? 31-day months, 30-day months, 28- or 29-day months?

 

I'd rather use days. A day is a day is a day.

---------------------------------------------------------------------------------------------
Maxims of Maximally Efficient SAS Programmers
How to convert datasets to data steps
How to post code
Respected Advisor
Posts: 2,810

Re: Calculate difference between dates in months with decimals

I guess that depends on how you define the word "easy".

 

The problem is that decimal months are not really defined; in fact, because some months have 30 days and some months have 31 days and some months have 28 or 29 days, I don't think you will find a unique answer, and I don't think there is anything programmed into SAS that will provide decimal months.

 

Nevertheless, you can create your own definition of decimal months and write data step code to make this happen.

--
Paige Miller
Contributor
Posts: 32

Re: Calculate difference between dates in months with decimals

Posted in reply to PaigeMiller

Okay, thanks for the suggestions. I'd hoped for a procedure or something. But for now I'm going to use this syntax;

DATA want;
SET have;
months=(end-start)/(365.25/12);
RUN;

 

Super User
Super User
Posts: 9,402

Re: Calculate difference between dates in months with decimals

That's both assuming an average for year and for month.  How accurate do you need it to be?  May not be a suitable calculation for some.

Super User
Posts: 13,300

Re: Calculate difference between dates in months with decimals

And ignores leap years.

Super User
Posts: 13,300

Re: Calculate difference between dates in months with decimals


hovliza wrote:

Hi! If I want to calculate the difference between months I use this syntax;

*months;
DATA want;
SET have;
months=intck("month", start, end);
RUN;

But you only get the months without decimals. Is there an easy way to get the months with for example 2 decimals?


Please describe exactly how you plan on using that fractional month part of the value.

Anything I have worked on that needed a different interval worked much better by dropping to an actual different interval, either weeks, biweekly period, days or even 5-day periods. That way at least handles 0.1month = one of .28, .29, .30 or .31.

Note that the intck and intnx functions supports multiples of the interval such as DAY3 or WEEK2 so you can easily specify a consistent period.

Ask a Question
Discussion stats
  • 6 replies
  • 268 views
  • 0 likes
  • 5 in conversation