That's a rather strange approach to take. Time::Seconds defines one month as 2,629,744 seconds (exactly one twelfth of a year). So by adding one month, you're actually adding 30 days, 10 hours, 29 minutes and 4 seconds. Which seems a strange way to approach this problem.

This issue becomes obvious if you print out the time parts of your object too.

#/usr/bin/perl

use strict;
use warnings;
use Time::Piece;
use Time::Seconds;

my $date =  Time::Piece->strptime( "2002-01-31", '%Y-%m-%d' );
print "\n Date:",$date->ymd, ' ', $date->hms;
$date += ONE_MONTH;
print "\n Date:",$date->ymd, ' ', $date->hms;
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Which displays:

Date:2002-01-31 00:00:00
Date:2002-03-02 10:29:04
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