use DateTime;

my $timezone     = 'UTC';
my $year         = 2012;
my $month        = 6;
my $day          = 12;
my $millisecond  = 3600000;  # 1.00 am

my $dt = DateTime->new(
	year       => $year,
	month      => $month,
	day        => $day,
	hour       => 0,
	minute     => 0,
	second     => 0,
	nanosecond => 0,
	time_zone  => $timezone,
)->add(
	nanoseconds => ($millisecond * 1_000_000),
);

print $dt;