Allow Only Future Dates in Gravity Forms Date Fields

$wpide_gf_notice_days = 1; // Days of notice required; 0 allows today.

add_filter( 'gform_field_validation', function ( $result, $value, $form, $field ) use ( $wpide_gf_notice_days ) {
    if ( 'date' !== $field->type || ! $result['is_valid'] || false === strpos( ' ' . $field->cssClass . ' ', ' future-date ' ) || empty( $value ) ) {
        return $result;
    }

    if ( is_array( $value ) ) {
        $value = implode( '/', array_values( $value ) );
    }

    $format = ! empty( $field->dateFormat ) ? $field->dateFormat : 'mdy';
    $parts  = preg_split( '/[\/\-.]/', (string) $value );
    if ( 3 !== count( $parts ) ) {
        return $result;
    }

    $map  = array( 'mdy' => array( 2, 0, 1 ), 'dmy' => array( 2, 1, 0 ), 'dmy_dash' => array( 2, 1, 0 ), 'dmy_dot' => array( 2, 1, 0 ), 'ymd_slash' => array( 0, 1, 2 ), 'ymd_dash' => array( 0, 1, 2 ), 'ymd_dot' => array( 0, 1, 2 ) );
    $idx  = isset( $map[ $format ] ) ? $map[ $format ] : $map['mdy'];
    $date = sprintf( '%04d-%02d-%02d', (int) $parts[ $idx[0] ], (int) $parts[ $idx[1] ], (int) $parts[ $idx[2] ] );

    if ( $date < wp_date( 'Y-m-d', time() + $wpide_gf_notice_days * DAY_IN_SECONDS ) ) {
        $result['is_valid'] = false;
        $result['message']  = $wpide_gf_notice_days ? sprintf( 'Please choose a date at least %d day(s) from today.', $wpide_gf_notice_days ) : 'Please choose today or a later date.';
    }

    return $result;
}, 10, 4 );