[me ~]$ perl datefail.pl --startday='-15 days' --endday='-14 days'
Start with Today
20151120T22:51-0700
Fix timezone
20151120T21:51-0800
Set the right day
20151105T21:51-0800
Strip the hours
20151105T00:51-0800
Strip the minutes
20151105T00:00-0800
[me ~]$ perl datefail.pl --startday='-19 days' --endday='-18 days'
Start with Today
20151120T22:51-0700
Fix timezone
20151120T21:51-0800
Set the right day
20151101T21:51-0800
Strip the hours
20151101T01:51-0700
Strip the minutes
20151101T01:00-0700

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;
use Date::Manip;
use Getopt::Long qw(GetOptions);

my $startDay;
my $endDay;

GetOptions(
        'startday=s' => \$startDay
        ,'endday=s' => \$endDay
);

my ( $startDDelta,$zeroStartH,$zeroStartHDelta,$zeroStartM,$zeroStartMDelta );

print "Start with Today\n";
my $dateObjStart = new Date::Manip::Date('now');
print $dateObjStart->printf('%Y%m%dT%H:%M%z') . "\n";

print "Fix timezone\n";
$dateObjStart->convert('US/Pacific');
print $dateObjStart->printf('%Y%m%dT%H:%M%z') . "\n";

print "Set the right day\n";
$startDDelta = new Date::Manip::Delta($startDay);
$dateObjStart = $dateObjStart->calc($startDDelta);
print $dateObjStart->printf('%Y%m%dT%H:%M%z') . "\n";

print "Strip the hours\n";
$zeroStartH = '-'.$dateObjStart->printf('%H').' hours';
$zeroStartHDelta = new Date::Manip::Delta($zeroStartH);
$dateObjStart = $dateObjStart->calc($zeroStartHDelta);
print $dateObjStart->printf('%Y%m%dT%H:%M%z') . "\n";

print "Strip the minutes\n";
$zeroStartM = '-'.$dateObjStart->printf('%M').' minutes';
$zeroStartMDelta = new Date::Manip::Delta($zeroStartM);
$dateObjStart = $dateObjStart->calc($zeroStartMDelta);
print $dateObjStart->printf('%Y%m%dT%H:%M%z') . "\n";