$dhms = DateTime->new(
   ...,
   time_zone => 'Etc/UTC',
   formatter => $formatter,
);
$dhms->set_time_zone('America/New_York');

##</code><code>##

my $formatter = ...;
my $utc = DateTime::TimeZone->new(name => "Etc/UTC");
my $nyc = DateTime::TimeZone->new(name => "America/New_York");

while (<>) {
   ...;
   $dhms = DateTime->new(
      ...,
      time_zone => $utc,
      formatter => $formatter,
   );
   $dhms->set_time_zone($nyc);
}