#!perl

use v5.14;
use strict;
use warnings;

use DateTime;
use DateTime::Format::CLDR;

my $parser = DateTime::Format::CLDR->new(
    pattern  => 'yyyyMMdd HH:mm:ss',
    on_error => 'croak',
);

my $format = 'M/d/y h:mm:ss a';

while (my $timestamp = <DATA>) {
    chomp $timestamp;

    $timestamp = $parser->parse_datetime($timestamp)
                        ->format_cldr($format);

    say $timestamp;
}

exit 0;

__DATA__
20040805 18:31:00
20050106 10:54:27
20050302 01:23:35
20100808 20:00:16
20110501 18:09:44
20110909 20:02:42
20130408 18:09:03