Calculate difference between dates in months with decimals

[hovliza]

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?

[Kurt_Bremser]

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.

[PaigeMiller]

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.

[hovliza]

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;

[RW9]

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.

[ballardw]

And ignores leap years.

[ballardw]

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@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.