Date:         Mon, 14 Feb 2011 16:29:48 -0500
Reply-To:     Tom Abernathy <tom.abernathy@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Tom Abernathy <tom.abernathy@GMAIL.COM>
Subject:      Re: many days in 13 months
Content-Type: text/plain; charset=ISO-8859-1

It depends on what you are doing. If you want the actual calendar dates and
the resulting variation in the number of actual days that can mean then use
the INTNX functions.
For research I usually use a constant number of days for all subjects.
Usually that is based on 30 days per month.  So a 6 month study is actually
an 180 day study.

- Tom

On Mon, 14 Feb 2011 16:08:06 -0500, Arthur Tabachneck <art297@ROGERS.COM>
wrote:

>Kim,
>
>I agree with data_null_, but had a slightly different application:
>
>data want;
>  set have;
>  if adm_date ge intnx('month',prg_enddate,-13,'sameday');
>run;
>
>HTH,
>Art
>--------
>On Mon, 14 Feb 2011 15:20:55 -0500, Kim Brown <kibrown@LADHS.ORG> wrote:
>
>>Hi all,
>>
>>How many days are there in 13 months?
>>What is the official way to calculate in SAS...?
>>
>>I was thinking 390 (30 x 13) or maybe 395 (365 + 30) or would it be best
>>to use datdif function.
>>
>>I have admitted date and program end date; I want to calculate within 13
>>months (keeping all visits within 13 month, dropping visits outside the 13
>>months and afterward the program end date.
>>
>>*this is a line from my code and it works...but I’m not sure if I’m
>>accurately calculating the 13 months...any suggestions will be
appreciated.
>>
>>if 0 LE (prg_enddate-adm_date)le 395
>>
>>Thanks,
>>Kim