package Datum;
use base qw( Exporter );

our EXPORT = qw ();

sub new {
    # neue Instanz erzeugen
    
    my $class = shift;
    $class = ref($class) if ref($class);

    # Datumswerte werden einzeln gespeichert
    my $self = {
                year => 0,
                month => 0,
                day => 0,
               };
    bless $self, $class;

    return $self;
}

sub set {
    # Datumswerte setzen
    # Parameter-Reihenfolge nach ISO
    
    my $self = shift;
    my ($y, $m, $d) = @_;

    $self->{year} = $y;
    $self->{month} = $m;
    $self->{day} = $d;
}

sub dateformat {
    # Datumsformat der Klasse liefern
    return "%y-%m-%d";
}

sub get {
    # Datum abfragen
    # ISO-Format
    
    my $self = shift;

    my $date = $self->dateformat();
    
    $date =~ s/%y/$self->{year}/g;
    $date =~ s/%m/$self->{month}/g;
    $date =~ s/%d/$self->{day}/g;
    
    return $date;
}

sub tounixtime {
    my $self = shift;

    my $unixtime = ...
    return $unixtime;
}

sub print {
    my $self = shift;

    print $self->get();
}

1;

package Datum::DE;
use base qw( Datum );

sub dateformat {
    return "%m/%d/%y";
}

1;

package Datum::US;
use base qw( Datum );

sub dateformat {
    return "%d.%m.%y";
}

1;

package main;

my $gerdate = new Datum::DE(2003, 10, 2);
$gerdate->print();

my $usdate = new Datum::US(2003, 10, 2);
$usdate->print();

sub _property ($$;$) {
     my $self   = shift;    # object
     my $attr   = shift;    # attribute to get or set
     my $setter = @_ == 1;  # is this method used as a setter?
     my $value  = shift;    # value for the setter

     # if we use "if (defined $value)" here, we can't set the values
     # to undef! So we have to use this:
     if ($setter) {
         my $old_value = $self->{$attr};
         $self->{$attr} = $value;
         return $old_value;
     }
     else {
         return $self->{$attr};
     }
} # sub _property


sub uhrzeit ($;$) { return shift->_property('uhrzeit',  @_) }
sub stunden ($;$) { return shift->_property('stunden',  @_) }
sub minuten ($;$) { return shift->_property('minuten',  @_) }
sub sekunden($;$) { return shift->_property('sekunden', @_) }
sub datum   ($;$) { return shift->_property('datum',    @_) }
sub tag     ($;$) { return shift->_property('tag',      @_) }
sub monat   ($;$) { return shift->_property('monat',    @_) }
sub jahr    ($;$) { return shift->_property('jahr',     @_) }
...

sub new {
my $objekt = shift;
my $referenz = {};
bless($referenz,$objekt);
return($referenz);
}

sub new {
  my $class = shift;
  my $referenz = {};
  bless($referenz,$class);
  return($referenz);
}

my @zeit = localtime(time);
$zeit[4]++; # monat beginnt bei 0 fuer januar
$zeit[5]+=1900; # jahr 0 ist 1900

sub _property ($$;$) {

sub _property ($$;$) {
     my $self   = shift;    # object