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st: Leap years in computing age


From   Stata Chris <statachris@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Leap years in computing age
Date   Wed, 26 Oct 2011 13:35:54 +0200

Hi Listers,

I would like to compute people's precise age in years on the day of an
important event.
Since I use the age as the forcing variable for an RDD, it is
important that I compute it as precisely as possible. In particular, I
want get it right whether individuals have or have not passed the
threshold number of years.

I have both the event day and the day of birth in Stata format, i.e.
in days after 1 January 1960.
Now I reckon I cannot just compute --gen age =
(eventday-birthday)/365--because of leap years.
So my approach was the following:

gen Age_years = year(eventday)-year(birthday)
gen Age_days  = doy(eventday) - doy(birthday)
gen age       = Age_years + Age_days/365
drop Age_*

But I'm wondering whether there is a more straightforward approach to
this, and indeed whether the above approach is correct?

Any suggestions welcome. Thanks a lot, Chris
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