Date:         Tue, 24 May 2005 10:53:22 -0400
Reply-To:     Kevin Roland Viel <kviel@EMORY.EDU>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Kevin Roland Viel <kviel@EMORY.EDU>
Subject:      Re: Question on Proc SQL
In-Reply-To:  <6F77AA8A6B0BAB43B9CA0CB8BAD9001B014BA6EA@njb-mail.bnj.2k.medarex.com>
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> But I have a question in regards to the difference
> (and it maybe a nave question) but would you know why the difference
> occurs?

Our concept of years of age typically mean the number of times something
reach the month and day of its birth in the cycle of years.  The
discrepancy results from the integer representation of an approximation.

Some years have 366 days and some have 365.  Since (approximately) every
four years has 366, we say that, on average, a year is 365.25.  Not every
fourth year has 366, for instance 1900.

The YRDIF() function, will correctly divide by 366 or 365 as appropriate.

Regards,

Kevin



Kevin Viel
Department of Epidemiology
Rollins School of Public Health
Emory University
Atlanta, GA 30322