Question

Apologies if this is a really simple question but I am interested in trying to reach an accurate answer and not just a “rounded” up answer.

My problem is: I know somebody is 27.12 on the 18th of March 2008 (random example). How can I calculate, to the nearest approximation, his date of birth. Age is always provided as a real number to two decimal points.

Answer 1

eumiro’s answer does the trick; the following, using the Time::Piece module (bundled with Perl since 5.10) is perhaps more maintainable.

use strict;
use warnings;
use 5.010;

use Time::Piece;
use Time::Seconds;

my ($date, $age) = ('2008-03-18', 27.12);

my $birthday = Time::Piece->strptime($date, '%Y-%m-%d') - $age*ONE_YEAR;
say $birthday->ymd();

This will get you within a few days of the actual birthday, due to the lack of accuracy (1/100 year) in the age.