use strict;
use warnings;

use DateTime qw( );

my $today = DateTime->today( time_zone => 'local' );

my $xmas = $today->clone()->set_month( 12 )->set_day( 25 );
if ( $xmas < $today ) {
   $xmas->add( year => 1 );
}

my $days = $xmas->delta_days( $today )->in_units( 'days' );
if    ($days == 0) { print( "Merry Christmas!\n"            ); }
elsif ($days == 1) { print( "Christmas is tomorrow!\n"      ); }
else               { print( "Christmas is in $days days.\n" ); }