? $zone->olson_version()
            : 'unknown';
        my $catalog_version = __PACKAGE__->catalog_olson_version();

        if ( $object_version ne $catalog_version )
        {
            warn "Loaded $real_class, which is from an older version ($object_version) of the Olson database than this 
installation of DateTime::TimeZone ($catalog_version).\n";
        }
    }

    return $zone;
}

sub _init
{
    my $class = shift;
    my %p = validate( @_,
                      { name     => { type => SCALAR },
                        spans    => { type => ARRAYREF },
                        is_olson => { type => BOOLEAN, default => 0 },
                      },
                    );

    my $self = bless { name     => $p{name},
                       spans    => $p{spans},
                       is_olson => $p{is_olson},
                     }, $class;

    foreach my $k ( qw( last_offset last_observance rules max_year ) )
    {
        my $m = "_$k";
        $self->{$k} = $self->$m() if $self->can($m);
    }

    return $self;
}

sub is_olson { $_[0]->{is_olson} }

sub is_dst_for_datetime
{
    my $self = shift;

    my $span = $self->_span_for_datetime( 'utc', $_[0] );

    return $span->[IS_DST];
}

sub offset_for_datetime
{
    my $self = shift;

    my $span = $self->_span_for_datetime( 'utc', $_[0] );

    return $span->[OFFSET];
}

sub offset_for_local_datetime
{
    my $self = shift;

    my $span = $self->_span_for_datetime( 'local', $_[0] );

    return $span->[OFFSET];
}

sub short_name_for_datetime
{
    my $self = shift;

    my $span = $self->_span_for_datetime( 'utc', $_[0] );

    return $span->[SHORT_NAME];
}

sub _span_for_datetime
{
    my $self = shift;
    my $type = shift;
    my $dt   = shift;

    my $method = $type . '_rd_as_seconds';

    my $end = $type eq 'utc' ? UTC_END : LOCAL_END;

    my $span;
    my $seconds = $dt->$method();
    if ( $seconds < $self->max_span->[$end] )
    {
        $span = $self->_spans_binary_search( $type, $seconds );
    }
    else
    {
        my $until_year = $dt->utc_year + 1;
        $span = $self->_generate_spans_until_match( $until_year, $seconds, $type );
    }

    # This means someone gave a local time that doesn't exist
    # (like during a transition into savings time)
    unless ( defined $span )